What game have you played most (in hours)?

payday 2 - 139h It's not that much if I compare to the others :p

Monster Hunter 3 for ~1300 hours.

in steam left 4 dead 2

1286 hours on Zombie Panic! Source

Football Manager 2013: 543 hours

Garry's Mod 238 hours.

Non Steam: Mass Effect 3 - 573 hours.
Steam: Civilization V - 368 hours.

On Steam: Cities: Skylines for...5 hours. lol

If I were to add up all my total time playing all 15 Pokemon games I have, I'd say around 2000-3000 hours total.

Dota 2 - 1 300 hrs

Steam:
Terraria - 1033 hours
Borderlands 2: 202 hours
(It's very convenient for steam to record exactly how much of my life is spent on games)

Non-Steam:
Super Smash Bros Brawl: Countless hours of my life
Minecraft: Countless hours of my life x2

Day of Defeat: Source - 3605 hours

Count by Steam
Euro Truck Simulator 2 404 hrs on record

Count by Raptr
Transformice (PC) 350 hrs

No idea which of those 2 are right...ets2 has only 346 hours on record on raptr

Skyrim 292h
Broderlands 2 and TF2 171h

cs 1.6 - 2736 hrs

Mass Effect 3 Multiplayer: 867 hours but i'm taking a break from lolstaggergeth atm

DotA 2 with 268 hours.

Team Fortress 2 with 1352 hours

On PC some 1000's of hours on LoL.

On console, uhm idk 100's of hours in many CoD's.

csgo 4k h and cs 1.6 7k h

In my 2nd steam account counter strike 1.6 - 4,582 hrs
But in this CS GO- 910 hrs

Probably Minecraft, more than 2000 hours. Best game ever

Football Manager 2013 - 160 hours

Team Fortress 2....1094 hours...

Lord of the Rings: Online. - Too many hours.

Warframe - 711 hours.