Right, for non-console games, I'd have to choose Elite, Doom and Halflife, because each of these games were "revolutionary". Ok, they've come out on consoles too, but they're still mostly home computer games. If you like playing PC/home computer games there's a lot of good games in all genres, but they're hard to compare to console games since most are a very different breed. I should mention X-Com, though, if it hasn't been mentioned already.
Right, on to consoles. Almost any games I could think of has already been mentioned, but it seems everyone forgets the GameBoy, even though a GameBoy Advance is possibly the console with the widest range of avaible games. Also, it has no region coding, so importing is easy:
Seiken Densetsu 1 (Final Fantasy Adventure in the US, Mystic Quest in EU)
Metroid 2 (IMHO better than the original)
Wario Land (Very different from most Mario games)
Zelda 4, Oracles and Minish Cap (Zelda 3 style perfected)
A host of SNES conversions
A host of NES conversions
Also a few Sega conversions
Metal Gear Solid (Because the NES/MSX games are too hard to get)
Final Fantasy Tactics Advance
Oh, and before I forget:
PC Engine Super CD2:
Ys book 1&2
Dracula X: The Blood's Rondo / Chi no Rondo
Advanced Variable Geo (If you want to make a shameless SF2 clone you might as well do it with style : )