Daudi,
Here's where some of my votes lie:
Action - Giants, MDK2, Thief 2, NOLF, RUNE, FAKK2.
RPG - Baldur's Gate II, Icewind Dale.
Strategy - Sacrifice, Ground Control, Homeworld: Cataclysm.
Sim - The Sims, Zeus: Master of Olympus.
Others - Motocross Madness 2, Tony Hawk 2, Crimson Skies...