Might and Magic VI : The Mandate of Heaven! (warning: pre-3dfx first person RPG) one of my favorite games of all time but i cant stand playing it these days.
for 3DFX goodness, get Might & Magic 7 which was also great.
how old are you? were you around for the first Diablo? Diablo II?
there are alot of Turn Based Strategy RPGs. my favourites: Heroes of Might and Magic series (2-5), Age of Wonders 2, King's Bounty from last year, Fantasy Wars (a 1C game) was great but can be frustratingly difficult at times. (it was inspired by Warhammer: Shadow of the Horned Rat)
hack'n'slashers: Diablo I & II, Sacred (i haven't played 2 yet), Titan Quest, Dungeon Siege (i only played 2 which was epic).
Square released The Last Remnant to the PC last year which is a great tactics based RPG if you like japanese games, and if you do, get Final Fantasy 7 and 8 for the PC as well.
all Bioware games.
what i am forgetting?