The game I've played for the most time is Age of Empires II (and its expansion) though I don't know how many hours but it's a lot XD

Gears of War 3 - over 1000 hours and still nowhere near Seriously 3.0

Monster Hunter Tri on Wii.

Around 1200 hours.

The Socom series. About a good 8 years spent on them.

I don't know how much time I spent playing Metroid Fusion. But considering the fact that I've been replaying the game over and over again since launch, and the fact that I've already put in 40 hours in it on the 3DS alone since the start of 2014, which is the platfrom I play it the LEAST on, I'd say I put in a huge amount of time in it XD

Pokemon Diamond 1000+ hours

Has to be Runescape. Easily put 5000 hours into that game.

CoD W@W: ~500 hours

Skyrim: ~300 hours

Fallout NV: ~150 hours

Dark Souls 2 over 200 Hours (Which is why it got boring to me :|)

I've spent around 399 hours on skyrim for pc and another 100 on the 360 version