(For the sake of this review, I used the PS4 version as my benchmark. I can't comment on the PS3/Xbox 360 versions.)
Even prior to the release of Peace Walker, Kojima teased the idea of Metal Gear Solid V. His team was busy developing a new game engine which would become known as the Fox Engine. The freedom of the Fox Engine would allow for a fully open world Metal Gear game, a notion which Kojima had been attempting to achieve since Snake Eater. With work on the Fox Engine wrapping up and the next generation of consoles approaching, the decision was made to make Ground Zeroes a cross-generational game.
Prior to the game's official announcement, Kojima went on record saying that his next game would deal with delicate, even taboo, issues which might not make the final cut in the game or which might be so shocking as to negatively impact the game's sales. Ground Zeroes was finally revealed in the summer of 2012 through a Japanese trailer which consisted of the game's opening cutscene. This was also the venue where Kojima announced that the game would be running within an open world setting, emphasizing player freedom to approach their objectives. It would also be available on a very wide release, with the PS3, PS4, Xbox 360, Xbox One and PC all being able to play the game.
Some confusion began to grow as the game's development continued. A trailer for a game called The Phantom Pain by "Moby Dick Studios" was quickly deciphered to be another Metal Gear game in simultaneous development. After some speculation, it was officially announced that The Phantom Pain was a part of Metal Gear Solid V, causing people to believe that this game and Ground Zeroes were going to be a single game. However, it was later clarified that they would be 2 separate games, with Ground Zeroes serving as a smaller prologue.
The game then began to encounter some major controversy. The long-time English voice actor for the Solid Snake and Big Boss, David Hayter, was replaced by Kiefer Sutherland. Fans bristled at this revelation and threatened to boycott the game, to no avail. Fans also complained about the game's addition of "reflex mode", which allows for a chance to eliminate guards after being spotted without setting off an alert, and a fast-regenerating health mechanic, both of which were seen as making Metal Gear too "casual".
During the game's initial release, the PlayStation versions received the "Déjà Vu" mission as a console-exclusive mission, whereas Xbox versions received the "Jamais Vu" mission. These two missions were timed console exclusives, which were unlocked for free for both consoles a few weeks after release. Naturally, the announcement about console-specific missions riled up some fans as well.
Probably the biggest source of controversy around the game though arose from Game Informer's Metal Gear Solid V cover story. In their commentary, they stated that the game was comparable to the Sons of Liberty demo, but paid for separately. Furthermore, they commented that they had completed the main mission in 2 hours, but some testers had run it in only 5 minutes. These comments caused fans to react extremely negatively, with people claiming that Konami expected them to drop $30-$40 for a demo with only 5 minutes of gameplay. These complaints were fresh in the public's minds when the game finally released in March of 2014 (although the PC version would not be released until December).
In the aftermath of Peace Walker, the UN has requested to inspect Mother Base for the presence of any nuclear materials. MSF initially turned the request down, but Huey took it upon himself to reverse the decision to try to make MSF appear to be a beacon of peace. As a result, Big Boss and Kaz prepare for the inspection by hiding ZEKE and their nuclear warhead, and evacuating civilians and heavy equipment offshore.
However, as they prepare for the inspection, Miller discovers that Paz survived her encounter with Big Boss. She has been captured by Cipher for interrogation and is now stationed in Camp Omega in Cuba. Hoping to rescue her, Chico sneaks into the enemy base, but is captured in the attempt. The Intel team attempts to discover Chico's location, but after some time a cassette tape is received which contains a distress call from Chico. Big Boss and Miller suspect that the request is a trap, but with the inspection bearing down on them and the sensitive knowledge held by Chico and Paz, they have no choice but to attempt a rescue.
As Big Boss infiltrates into Camp Omega, Skullface, the leader of the Cipher special forces unit XOF, departs by helicopter and then heads out to sea to perform the UN "inspection". Big Boss witnesses the helicopter convoy heading out and then moves to retrieve the prisoners. Making his way through the base, Big Boss locates Chico and then takes him to the shoreline for extraction via helicopter. Chico laments that Paz is already dead, giving Big Boss a cassette tape of her being tortured. Undeterred, Big Boss heads back into Camp Omega to locate Paz. He finds her in the basement of the Admin building, chained up in the boiler room. He sneaks her back out to the extraction site and then heads back towards Mother Base with the two rescued prisoners. However, on the way back, Chico discovers that Paz's gut has been stitched up. Big Boss realizes that she has been rigged with a bomb and orders a medic to come inspect her. After a painful surgery without anesthetic, the bomb is extracted and thrown into the ocean.
Contact is soon lost with Mother Base though. When they arrive, they see that the base is on fire and that many of the struts have collapsed. The helicopter lands on one intact strut, which allows Big Boss to save Miller and a couple other soldiers before evacuating. Miller blames Paz for the destruction of MSF, but she stands up and reveals that there is a second bomb before jumping out of the helicopter and exploding. Despite her sacrifice, the blast radius knocks the helicopter out of control and sends it careening into the path of an XOF helicopter, causing the two aircraft to crash and putting Big Boss into a coma...
GAMEPLAY & DESIGN
First off, I have to say that in a lot of ways it is fair to call Ground Zeroes a paid-demo, as it really is a stripped-down tech demonstration for the game's main act. That said, it does have quite a bit of content to experience which helps to justify its stand-alone price point. For one thing, there are 7 different missions in this game which can all be replayed and experienced in a number of different ways. The main "Ground Zeroes" mission alone should easily take up 1.5 to 2 hours to beat on a first playthrough. In addition, unlike many open world games, all of the side-ops are well worth trying out. They all have their own interesting little stories and fairly unique objectives which make them both fun and challenging. For my own part, I have probably sunk at least 8+ hours into this game.
Of course, the "Ground Zeroes" mission is where most of the gameplay lies, and it is thankfully very fun. It is reasonably lengthy and offers a ton of player freedom. While you're supposed to rescue Chico first, you can actually choose to go for the more difficult approach and rescue Paz first, which adds a whole new angle of challenge and difficulty to the mission. The other side-ops change up the gameplay quite a bit, tasking you with eliminating targets, retrieving intel or even killing body-snatchers.
In terms of mechanics, Ground Zeroes plays similarly to Guns of the Patriots in many ways. The radar and all associated systems have been completely eliminated, meaning that reconnaissance and situational awareness are now crucial to stealthy gameplay. The controversial reflex mode is a major boon in this department - with most of your aids now excised, having that last ditch effort to land a headshot is extremely helpful, without feeling absolutely broken either. Of course, if you're just too damn "hardcore" for this pansy-ass bullshit, then you can just turn it off. And then eat some nails, presumably.
If you do get stuck in a straight-up gunfight, Ground Zeroes' combat is extremely refined. Gunplay is very fun and smooth, not featuring any of the stuttering which was common in Guns of the Patriots. Enemies' animations when they get hit are notable for how surprisingly good they are, with shots to various parts of the body staggering them in that direction. CQC has also seen another makeover, with standard combat chains actually being a viable option, rather than having to rely on chokeholds and hold-ups to get anything done. You can also steal enemy vehicles, such as a jeep, truck or LAV (which has always proven extremely useful to me when extracting Paz).
Despite the game's philosophy of providing player freedom, there are some annoying design decisions which go against this idea. Probably most importantly, the lack of ability to customize your loadout is a major problem which hurts replayability. Sure, you get some bonus weapons at the start of the mission when you replay it, but they're very limited in variety. There's also just a lack of meaningful weapon variety in general, with nearly everything being procure-on-site. The game also locks its 2 bonus side-ops, "Déjà Vu" and "Jamais Vu", behind a collectible hunt. This is rather annoying because this locks off a good 30+ minutes of content (for just a single playthrough) which most players aren't going to bother to unlock. It also doesn't hurt that "Jamais Vu" is arguably the funnest side-op in the whole game.
STORY & CHARACTER ANALYSIS
Like most Metal Gear games, Ground Zeroes opens up with a very impressive cutscene which shows off a Alfonso Cuarón-style continuous tracking shot which shows the player around Camp Omega. Here we are introduced to all of the key players, including the enigmatic villain of the game, Skull Face. Most of the story is told in a rather simple, straightforward manner, but the story itself is fairly compelling. A lot of supplementary information related to backstory is sectioned off in the game's optional and collectible cassette tapes (including all of Paz's secret tapes from Peace Walker). While it will take you over an hour to listen to all of the tapes, I would definitely recommend that you do so, as they fill out the whole political situation surrounding the game's story very well, lend it additional gravitas and show the various characters' motivations. The interrogation cassettes are also rather important as they flesh out Skull Face's character, especially considering that he is basically a shadowy figure off-screen for the whole game.
Of course, there is one very lengthy and difficult-to-listen-to cassette tape which details the torture inflicted upon Chico and Paz, which features Paz being gang raped by the soldiers, having Chico be forced to rape Paz (with Skull Face twisting it into a sick reward for the boy, who you must remember had a crush on her) and having Skull Face be heavily implied to insert a bomb into Paz's vagina. The amount of suffering that she endures is unimaginably awful, and the fact that this sequence is an unlockable "reward" caused a fairly big controversy. Claims that depictions of sexual violence were being used as a "reward" for the player were rather overblown, as I'm sure that most players will concede that these are hardly a "reward" at all, but rather plot explanation. You could definitely argue about the necessity of such depictions, but this was one controversial aspect of the game which I think was overblown from people who didn't actually play the game.
It's also worth realizing that all of the torture inflicted on Paz ties into this game's main theme, which revolves around the ethically bankrupt actions carried out by governments. Camp Omega is clearly intended to be a representation of Guantanamo Bay detention camp, and the tortures inflicted on the characters are meant to be a commentary on the moral shadiness of American anti-terrorism methods. The game compounds this idea with its theme song, "Here's to You" (which was previously used in Guns of the Patriots' closing credits). The song is about a pair of anarchists who were executed by the American government in the 1920s, who are believed to have been executed for their political beliefs rather than any actual actions the pair might have committed. The song plays at a few key moments throughout the game, particularly during the opening and when Paz is being tortured by Skull Face.
With these themes in mind, I don't believe that this game is truly about Big Boss, as it may seem to be at first glance. In my opinion, this game is all about Paz. She is the one invoked by "Here's to You", the martyr who is killed by the government, and the only character who has a real arc in the game. In her own audio tapes at the end of Peace Walker she reveals a conflicted desire to turn on Cipher and live as a true student of peace, but those dreams were lost. She also revealed a dislike of Chico, but when the two of them are being tortured she seems to warm up to him a lot. She even comforts him throughout their torture, even when he is forced to rape her and even though she is receiving the brunt of their depravity. She also refuses to break throughout the interrogations until Skull Face presents her with an offer - Big Boss's life for Zero's location. Betrayed by her own organization and perhaps looking to redeem herself for her previous actions, Paz sacrifices her own life to help ensure Big Boss's survival. This is further demonstrated by her willingness to throw herself out of the helicopter at the end when she realizes that they didn't find the second bomb planted on her. All of the suffering she is inflicted with makes Paz seem like something of a Christ-figure in this game. It's easy to miss all of these plot points though if you don't dive into the game's audio tapes. Without them, this is a simple story about how Big Boss rescues a couple of targets. With them, this is a story about Paz's struggles, her choices, her strength in the face of evil, and her defiance until the end.
Ground Zeroes suffers a bit as a prologue though. If the purpose of a prologue is to set up the events which unfold in the greater story, then Ground Zeroes is rather inadequate. Judged from this game alone, you'd think that The Phantom Pain would be primarily concerned with the dark side of nationalism/government control, but those plot points are never raised again. The only way that the two are really connected in a meaningful way is that it sets up Big Boss's desire for revenge, but if you want a really tight narrative (especially in a two-part release) then you should at least try to work in the other themes in the game, rather than just the simple motivations. This is, of course, not entirely this game's fault, but it is a strange point which makes some of the more fantastical elements of The Phantom Pain more awkward, especially after the extreme seriousness of Ground Zeroes.
All-in-all, Ground Zeroes is a very fun, but limited game. Questions of the length and value of the game persist long after its release. It is definitely a fun experience, but it really does feel like a rather large demo when all is said and done. Luckily, it is also quite cheap to acquire these days, making questions of value less of a deal-breaker for more people. For my own part, I'd recommend checking it out before jumping on board with The Phantom Pain, but be sure to experience the main story and the side-ops for maximum enjoyment.