Baldur's Gate Complete (Shadows of Amn/Throne of Bhaal etc) [lost count due to replaying different char builds]
Icewind Dale: Ultimate Pack [lost count due to replaying different char builds]
Age of Empire 2 [only once I think through the single player campaign, mainly for the LAN multiplayer with my friends]
StarCraft: Brood War [only once for the sake of knowing what my friends are talking about, else all MP]
Rome: Total War Gold Edition [countless]
Medieval: Total War (normal edition) [countless]
Shogun: Total War Warlord Edition [countless]
Romance of the Three Kingdoms [completed as Sun Quan, Liu Bei, Kong Rong, Gongsun Zan, Meng Huo, and personal characters]
Left 4 Dead 1 and 2 [completed all campaign maps, lazy to download custom maps]
Star Wars: KotOR 1 and 2 [at least once for both]
Civilization 2 [a few times, usually restarted halfway once the cities gotten too large]
Cyber Empire [countless]
King of Dragon Pass [countless]

Mass Effect 1 and 2 [at least twice for each, mainly to play out both gender options]
Titan Quest + Immortal Throne [if farming Hades = end of game, then countless of times completed]

Borderlands [completed once for main campaign + Zombie Isle DLC, insufficient time for the remaining DLCs]
Team Fortress 2 [too many hours spammed in this game to say that I haven't completed it ]
Shining Force 2 (Sega Emulator) [once for nostalgia sake]
Serious Sam: First Encounter HD [once, after that I fainted from headaches]
Civilization V [completed as English and Japanese before, insufficient time for the rest of the civs]

Audiosurf (Steam) - completed a few rounds for Summer achievement, and that's it.
Dungeon Defenders (Steam) - I blame Skyrim and TF2 for taking up the time slots.
Killing Floor (Steam) - insufficient players!!!
Serious Sam: Second Encounter HD (Steam) - afraid of headaches.
Hitman: Blood Money (retail) - lazy to complete it.
The Witcher Enhanced Edition (Steam) - disliked the combat/fighting style.
King Arthur: The Role-playing Wargame (Steam) - downloaded but never started it up.
Overlord 1 and 2 (Steam) - halfway thru and TF2 released new hats/weapons.

Wizardry 8 [once, regret not buying it]
Civilization 3 and 4 [several times]
Dungeon Keeper 1 and 2 [once, the rest MP and random versus CPU/COM maps, another game regretted of not buying]
...and plenty more lol.