This has been mentioned in other posts, but I will reiterate it here. Gran Turismo is something else. The realism is untouched by any racing game to this point. But Playstation has a lot more to offer. Here's a list of games in different genre's that I have played and would highly recommend.
Action/Adventure- Tomb Raider (the original is the best IMO), Metal Gear Solid
RPG- Final Fantasy Tactics, Final Fantasy VII, Vandal Hearts
FPS- All the one's from the PC's. Goldeneye for N64 is really cool too.
Suspense/horror- Resident Evil, Resident Evil 2, Silent Hill
Sports- Madden 98, NBA Live 99, FIFA (any one of 'em are good)
Racing- Gran Turismo, Rally Cross,
Fighting- Tekken 3 (This game ROCKS! If you have PSX, and you haven't played this then you better go out and rent it cause it is WILD!)
I know Hemlock meant Computer Games, but I don't have too many of those. Only Diablo, Myst, Need for Speed, and well, AoE/RoR.