Pretty much every game I owned before 2000. I had more time than I did games. If I tried to actually complete the list, I'd probably be here all night listing all the shareware titles, C64 games, and random stuff I borrowed from friends.
In the last 10 years, though? Not so much.
Diablo 2
Civilization IV and V (if those even count)
Dynasty Warriors 6 (I played this long enough to regard it as multiple beatings)
Dynasty Warriors 5
Amplitude
Defense Grid
every Guitar Hero and Rock Band
Borderlands
Katamari Damacy
Ogre Battle (on simulator)
That's probably a reasonably exhaustive list.