I was never excellent at the original Metal Gear game. I could get to the room with the super computer but never blow it up. I heard that there were a lot of things you had to do before you would be told how to blow it up and then you could do it (5 plastic explosives I believe, once you were told how). Anyway I could never get told because I did not know what to do.
A friend of mine had beaten it and I asked how. He said, as soon as you go into the room with the supercomputer, go immediately right without advancing into the room at all (run into the wall) and you will be transported into the room with Big Boss to fight him (there is a door on the right of the computer room but it would not open). I finally figured it out that it was to run into the wall as mentioned previously (my friend was vague). Then you can beat Big Boss and go up the elevator while the whole place explodes (normal game ending). But you do not have to beat the computer, etc. Basically any time after you get card 8 and the rocket launcher you can do this and "beat the game."
Jus thought I would share that, I found a walkthrough on the internet years later with no mention of this loophole, specifying that you had to do this and that to beat the game. My personal experience of finding a "bug" in a game.