Where the hell is the Turn-Based Strategy option?
That said, I tend towards RPGs overall(Avernum series, Deus Ex, Oblivion/Morrowind and their expansion packs, Arcanum, Fallout, ect) though turn-based strategy games come in a very close second(Alpha Centauri[damn near my all time favorite game], Civilization III/IV, Galatic Civilizations II).
I've also enjoyed a fair number of first/third person shooters(Half-Life series, Max Payne[which becomes quite the beat 'em up with the addition of the Kung Fu mod], Deus Ex[it's worth mentioning twice], GTA III, Postal 2).
You're also lacking a space/flight option(Freelancer, Freespace 2) as they're worth their own category.
The occasional racing game is often a good change of pace(Need for Speed : Underground was one of the funner ones).
Never been big on platformer games, but Psychonauts was one of the few games I regret not paying full release price for.
Outcast fills in for Action/Adventure, and offers significant compitition for all-time faveorite game.
And those are all the big ones I can think up off-hand.