What game did you play to most?

The Binding of Isaac (although it's probably FO:NV without the idling).

Most hours spen in cs 1.6 too. I don't play it too much now.

Sonic Generations, just 7 hours.
Pathetic, isn't it?

My steam account says it is The Last Remnant - 240 hours and i don't know how it happened :)

Half-Life

My most played game is Star Trek Online and as of this comment I am up to 834 hours according to Steam.

APB Reloaded
1.8 hrs / 1,059.9 hrs

1108 hours in GMod,a couple hundred of those are probably idled though.

Then,258 hours in Team Fortress 2

Then,100 hours in Counter Strike Source

Thanks a lot Valve/Garry :)

Edit: This is all on one account too,I've had a couple others,would probably go up to 2000 hours in GMod,400 in CSS,and 600 in TF2

Civilization V 157.9 h

154 hours of Dungeon Defenders, 60 Hours of Isaac, 35 Hours of Awesomenauts, 8 Hours of Borderlands, 7 Hours of Portal 2, 6 Hours of Recettear

Jade Empire-25.8 hours. The in-game save file says closer to 19 hours though, choose which you want to believe.
I've spent more time in Frozen Synapse then that though, but most of it was in offline mode so it wasn't recorded.

Probably World of Warcraft, it really racks up over the years.
Singleplayerwise, I think I played Prince of Persia SoT Trilogy over and over at least 6 times.

Also clocked 9 days in Diablo 3, but it could be so much more if I'd have a proper PC.

2.599 hours on Counter-strike: Source, off steam i have about 5k hours on Unreal Tournament.

889 hour dota2

447 hours of TF2...
but the game that i play mos in all life... probably Q3 or musou warriors orochi from PS2

I sunk 3000+ hours into oblivion, but that wasnt on steam op didnt say where lol

Close to 500 hours on Killing Floor

TF2 (1000 hours, 500 before steam time logs came in) way before, Now its Arma (No! Not fucking day fucking z"ed") for the past year or 2.

cs1.6, about 2k hours.

In Steam, A.V.A - 1026h.

150 Football Manager 2012 =)
and I think this year i should have played more

Heroes of Newerth : 1739 hours (about 100 hours of idling)

Call of duty 2 : 1730 hours - I don't regret an hour spent on this one ! back in the day i was in top50 clans in eu (CB) , was fun and stuff. Then cheaters came and ruined whole community...Ah well

At moment skyrim, but will change soon!

Dota2 900 hours and a litlle more