NES Metal Gear 1 is probably the worst, but I guess that doesn't really count.
Seriously though, that game is terrible. You're basically guaranteed to get spotted at least a few times... in the starting area. To even GET to Outer Heaven, you have to ride a confusing series of trucks. There isn't even Metal Gear at the end, just a computer. At least it's not Snake's Revenge.
Which reminds me: Snake's Revenge accidentally predicted the future. Er, past. Snake doesn't actually get revenge on anybody in the game; all the characters are new, Big Boss (er, [
Venom Snake]) died in Outer Heaven, and Snake went the opposite direction he went in the real sequels; instead of being the broken wreck of a soldier he is in later games, Snake's Revenge's manual instructs you to write your name in as Snake's real name and says he's a combination of "Rambo, James Bond, John Wayne, and Lawrence of Arabia."
Rather, the person taking revenge is Big Boss, who comes back from the dead and transforms into a purple cyborg who breathes fire because he "WANTS REVENGE". The title just seems like a generic sequel title akin to "Son of Godzilla" or "Bride of Frankenstein", likely written by somebody who never played the game... until 14 years later, it's revealed Big Boss was the original Snake, and suddenly making the title make sense.
Seeing as how I have the HD collection, I think I'm going to just play through the Big Boss storyline in order. Considering Solid Snake has to his name the oldest MGS game, the one with the most nonsensical plot, and the one with the longest cutscenes, I can probably pass.
Well, you do already have MGS2...