PC Games 1990-2000
Horror: WaxWorks, Alone in the Dark
RPG: Dark Sun, Blade of Destiny, Ultima Underworld, Eye of the Beholder, Lands of Lore, Stonekeep, Diablo, Baldur's Gate, Icewind Dale
Sci-fi: System Shock, Terra Nova, Mechwarrior: Mercenaries, Wing Commander, Tie Fighter
Strategy: Dune 2, Master of Orion, Command & Conquer, Total Annihilation
Adventure: King's Quest, Space Quest, Maniac Mansion, Monkey Island, Blade Runner
FPS: Wolfenstein, Doom, Quake, Future Shock/Skynet
PC Games 2000-2006
Horror/Adventure: The Thing
RPG: Neverwinter Nights, Arx Fatalis, Morrowind, Oblivion
Sci-fi/FPS: Alien vs Predator 2, Mechwarrior 4: Mercenaries, Doom 3, Quake 4, Farcry, Battlefield games
Strategy: Ground Control 2
I don't remember any others right now, but all of these are classics.