(Note, I will be reviewing this game based on the HD Edition re-release on PS3, which I beat on Original difficulty to try to get the "authentic experience". I will also mention that I hadn't completed Metal Gear before this playthrough and was relying heavily on a guide, so my review is probably going to be somewhat skewed as a result.)
A young Hideo Kojima joined Konami in 1986 as a planner, but was having trouble getting his ideas completed. After the cancellation of a game he had been working on for six months, Konami asked Kojima to come up with a war game for them for the MSX2. Due to hardware limitations, Kojima was becoming frustrated by the lack of bullet and enemy sprites he was able to get on screen at once. A massive film buff*, Kojima took inspiration from The Great Escape and decided to make a game where the goal was to avoid combat as much as possible. Konami wasn't too keen on this idea, and Kojima nearly left the company due to internal friction, but eventually these differences were sorted out and the game was completed and released in 1987.
Shortly after Metal Gear's completion, the game's code was given to a separate team to release a NES port without Kojima's knowledge or consent. The heads at Konami specified that they wanted this version to be as different as the team could make it, and gave them a 3 month development window. The resulting game was markedly different and much shoddier, with notoriously bad Engrish and with the game's Metal Gear boss being replaced by a supercomputer, among other questionable changes. This already-inferior port was further tarnished by being ported again to the shoddier Commodore 64 and MS-DOS, resulting in two practically unplayable versions of the game.
As I played the PS3 re-release, which is very slightly changed from the MSX2 version, I can't really give much commentary on the NES port or its bastards, but I will link to this review for an analysis if you're interested. For quite some time though, the NES port was the only version of Metal Gear available in North America, and actually received its own non-canon sequel, Metal Gear 2: Snake's Revenge. Suffice to say, that game will not be covered in this retrospective.
In 1995, intelligence reports begin to leak out that there a weapon of mass destruction has been constructed within Outer Heaven, a mercenary fortress in South Africa. The US government gets Big Boss to send FOXHOUND operative Gray Fox to infiltrate their fortress and determine if their intelligence was correct. Gray Fox does locate the weapon, but is captured by Outer Heaven forces, his last transmission being an ominous utterance of "Metal Gear..."
Shortly after, FOXHOUND member Solid Snake is sent into Outer Heaven for his first mission by Big Boss. He is instructed to locate and rescue Gray Fox and then find what he can about Metal Gear. After freeing many prisoners of war, including the local resistance leader Kyle Schneider, Snake is pointed to Gray Fox's location. He is intentionally captured and then breaks into Fox's cell, where he is told of Metal Gear's capabilities: it is a walking, nuclear-equipped tank, but luckily is still inactive. Fox instructs Snake to locate Metal Gear's captive creator, Dr. Pettrovich Madnar, in order to discover how to destroy it.
After fighting his way through Outer Heaven, including taking down some of the group's lieutenants, a Hind D, a battle tank, a bulldozer and an imposter Dr. Madnar, Snake makes his way to the real Dr. Madnar's cell with the help of the resistance member, Jennifer. However, Dr. Madnar refuses to help Snake until his daughter, Ellen, is saved. A resistance member, Diane, advises Snake on where to find Ellen, and he dutifully hurries to rescue her. After fighting through more of Outer Heaven's soldiers, Ellen is rescued and Snake returns to Dr. Madnar. He tells Snake that Metal Gear is in the 100th basement floor 20km north and would need to place plastic explosives on its feet in a specific order to destroy it.
Determined to complete his mission, Snake hurries to Metal Gear's hangar, but is constantly ambushed by enemy troops and nearly led into a series of traps due to poor intelligence from Big Boss. Eventually, Big Boss orders him to abort the mission entirely. Disregarding Big Boss's orders, Snake enters Metal Gear TX-55's hangar and places the explosives on its feet as per Dr. Madnar's orders. Metal Gear is destroyed and a self-destruct sequence is initiated. Snake hurries to escape, but is confronted by Big Boss! Big Boss tells him that Snake had been sent in to acquire false information, but he had gone too far. The pair fight, but Snake defeats his mentor and escapes Outer Heaven just as the facility is destroyed.
However, as the credits draw to a close, Big Boss vows revenge on Snake for destroying Outer Heaven...
Guards in this game are incredibly stupid. In addition to completely forgetting you if you leave their screen most of the time, when they are alerted they will run around randomly and bump into objects as they try to home in on you, meaning you can hide behind a corner and punch them to death easily when they finally manage to get to you. When they are unaware though, they follow a standard, set patrol pattern which will feel instantly familiar to Metal Gear franchise vets and makes for some fun gameplay. The game also features jetpack enemies, which can be panic-inducing the first few times you encounter them. They're very fast and hard to actually hit, making combat with them inadvisable. Luckily, they only show up at parts where you should run like hell away from them, but if you aren't following a guide then I imagine they could be a major headache.
The game also has quite a few distinct bosses which, while very simple and easy, are quite fun and often feature the signature Metal Gear gameplay-twists that make these battles so exciting... plus in the original release they have some pretty hilarious Engrish names like Shoot Gunner and Coward Duck. I think my favourites were the fights against a tank and the fight with Shotmaker (aka Shoot Gunner), in which you start the battle with no weapons. Also of note is that the MSX version of the game has a showdown with a non-active Metal Gear. This fight is a bit disappointing and artificially challenging - you have to put plastic explosives on its legs in a specific order to do any damage for some inexplicable reason. Meanwhile, laser cameras shoot at you, with each shot taking off half of your health bar! It's not particularly challenging, especially if you've farmed for rations prior to the fight, but it is certainly noteworthy as the first battle with Metal Gear in the entire series. This is then capped off with a fight against "Big Boss" himself, although it is quite easy as he doesn't seem to know enough to not run into your rocket launcher's shots.
Put simply, Metal Gear was obviously never intended to become the first chapter in an epic saga. It was clearly just meant to be a fun, 80s-style action story, including the requisite "traitorous commander" twist. Considering that the game's art (and the art of its sequel) use images of action movie stars as the basis of Solid Snake and Big Boss, it seems fair to suggest that this was the intent. The concept of Metal Gear itself though is quite an interesting one for such an otherwise simple game and one which definitely deserved expanding upon for its own merits. Metal Gear TX-55 has a really cool, unique, old-school design which I wish that Peace Walker and The Phantom Pain would have tried to emulate.
As I've hopefully made clear, Metal Gear is a very simple, if at times frustrating, game with a lot of old-school charm and a great (if sparse) 8-bit soundtrack. Not not sure that everyone will have what it takes to get through it, but completing it with a guide should only take around 3-4 hours. In fact, now that I have gotten through the game and have acquired the necessary skills to succeed, I'm kind of itching to play it again - this time, without a guide. Considering that I still have to play through the rest of the series to get this retrospective done, it probably won't happen, but if that isn't a testament to how fun this game is almost 30 years later, then I don't know what else will sway you.