What game have you played most (in hours)?

Call of Duty: World at War- 208 logged hours and counting

Killing Floor - 2142 hours

Edit: I think with SAM (Steam Achievement Manager), you can use it to set a number of hours in any Valve game.

Killing Floor - 230h

Skyrim 200 somethign hours

Skyrim 202h

Diablo 2 Lord of Destruction. Easily over 1000 hours. :>

Diablo 3 2000+ hours

x3 albion prelude with battlestar galactica mod. around 450 hours

1st Binding Of Isaac Rebirth - 45 hours
2nd Castle Crashers 12.5 hours

dota 2 15864
I should turn my computer off more often....

Probably Super Smash Bros. Melee, had like 800 hours

Dark Souls: Prepare to Die Edition 143 hours.

Dragon Age: Origins - Ultimate Edition 102 hours.

Dota 2 with 158 hours and second CS: GO with 152 hours and still counting

CS:GO with around 450

Dota - Like 1050 hours

Currently: Natural Selection 2 - 671 hrs & Far Cry® 3 - 227 hrs. Skyrim would be #1, but at the time I didn't have internet at home so my hours weren't counted :(

Don't Starve – 233 hrs.

StarCraft 2 - 2413h
Path of Exile -1128h

Want more? :D

I haven't this registered in my account, but I played like 10000+ hours of CS 1.6 ;)

Civ V - over 500 hours

Skyrim 375 hours. Then FF14 with 293, then Oblivion with 178.

Dota 2 - 1,258 hrs on record
Path of Exile - 1,253 hrs on record
Skullgirls - 983 hrs on record

My most played game is Counter Strike GO with 286 hours, the second is Skyrim with 146 hours, but consider that in those 146 hours i have only started the main quest ( i just started the Greybeards quest line and i still haven't joined the faction) i just did some side-questing :D

Total War: Rome II