LOL, 1 gunung I need to count since I start play from Win95 era..

Listed game mostly completed once or so, unless stated

Red Alert 1 + Aftermath expansion
Red Alert 2 + Yuri Revenge expansion
Red Alert 3 + Uprising
Command & Conquer 3 + Kane Wrath Expansion
Command & Conquer 4
Grim Fandango - more than 3 times
Warcraft 3 + Frozen Throne expansion
StarCraft
StarCraft 2
Diablo 1
Diablo 2 + Expansion
Star Wars Dark Force 2
Star Wars Jedi Knight 2 - 2 times
Star Wars Jedi Knight: Jedi Academy - 3 times
Star Wars - KOTOR - 2 times
SW: Force Unleashed
SW: Force Unleashed 2
Star wars The Clone War : Republic Heroes
Star Wars KOTOR 2
Doom 3
Doom
Decent (DOS Game)
Duke NUkem 3D (DOS)
Duke Nukem Forever
Bug Too (DOS)
MEgaman X3
Megaman X4
FEAR 1
FEAR 2
Company of Heroes
Medal of Honor Allied Assault + Spearhead + Breakthrough
Medal of Honor (2010)
Medal of Honor: Airborne
Call of Duty + United Offensive
CAll of Duty 2
COD: Modern Warfare
COD: Modern Warfare 2
COD: World at War (1x SP 1x Co-op)
COD: Black Ops
BioShock
BioShock 2
Metal Gear Solid 2 Substance
Serious Sam First Encounter + HD
Serious Sam Second Encounter + HD
Serious Sam 2
Tomb Raider
Tomb Raider 2
Tomb Raider Underworld
Tomb Raider Anniversary
Tomb Raider Legend
Lara Croft and the Guardian of Light
Warhammer 20k: DOW2 + all Expansion
Age of Empire
Age of Empire 2
Age of Mythology
World in Conflict
TLOTR: Return of the King
Guitar Hero 3 - replay countless times
Guitar Hero World Tour - replay countless times
Zeno Clash
Brothers in Arms
Hellgate London
Portal
Portal 2
Half Life
Half life 2 +ep1+ep2
NeverWinter Nights
Bulletstorm
Mirror Edge
Crysis + warhead - 2 times
Crysis 2
Fable
Red Faction
Red Faction 2
Red Faction Guerilla
Red Faction Armageddon
Dead Space
Dead Space 2
Devil May Cry 4
Halo
Halo 2
Dark Messiah
FarCry
Gear of War
Batman Arkham Asylum
Dungeon Siege 3
Prototype
Dragon Age + awakening
Dragon Age 2
Mass Effect
Mass Effect 2 - 2 times
Rainbow Six Vegas
Rainbow Six Vegas 2
Battlefield Bad Company 2
Battlefield 3
Unreal 2
Unreal Tournament 3
Saint Row 2
Dead Island
Borderland
Velvet Assassins
Hitman 2
L4D - too much till cant count
L4D2 - same as above
Resident Evil 5 - 2x times in Co-op
Fallout 2 - 3 times
Fallout 3
Fallout New Vegas
Titan Quest + Immortal Throne
Divinity 2 Dragon Knight Saga
NOX
Imperialism
Contructor (DOS)
Syberia
NFS Underground
NFS Underground 2
NFS Most Wanted
Alien Breed
Alien Vs Predator 2
Alien Vs Predator
Beyond Good and Evil
Prince of Persia Sand of times
Darksiders
Deus Ex 2
Lost Planet
Mafia 2
Operation Flashpoint Dragon Rising
Transformers: War for Cybertron
PainKiller + Battle out of hell

... to be continue