I have a lot:
(In no particular order)
Oblivion IV Elder Scrolls.
Sims(all of them, 1-3)
Age of Empires II
Age of Mythology
Stronghold
Need for Speed III - Hot Pursuit
Excite Truck
Crazy Taxi
Roller Coaster Tycoon
Super Smash Brothers! All of them
Combat Fight Simulator(I know, great name)
Blazing Angels
Guitar Hero/Rockband, especially the Beatles one
Battlefield 1942
Final Stretch
Zoo Tycoon
Nancy Drew series!
Adobe Creative Suite 4! Oh wait. It can be a game if I want it to.
Mario Kart for the Wii
Pokemon! I have all of them up to Leaf Green.
Legend of Zelda series, especially Ocarina of Time
SPYRO THE DRAGON!
and Crash Bandicoot
DDR
Animal Crossing
Those are just the favourites
I have so many systems, too: Playstation 1 and 2, N64, Gamecube, Wii, an excessive amount of PCs, DS, GB Advance, GB Colour, even a big grey one.