You know I was looking at this and thinking how much time I have spent gaming. It was fun to do, but damn, was it a lot of time.
Lots of strategy here:
Civilization V: 941 hours on record, though I know I have probably over a hundred hours of unrecorded gameplay.
Civilization IV: 574 hours on record
Crusader kings II: 441 hours on record
Europa Universalis IV: 371 hours on record
Xcom: Enemy unknown: 281 hours on record
Other games I've played that have similar hours on record are call of duty: modern warfare 2 on xbox 360 (I can reasonably estimate something like 500-600 hours), pokemon heartgold (somewere around 275 hours) and mass effect 2 (200-300 hours). I have no way of knowing how much time I've put into the various halo games, crysis, minecraft, super smash bros brawl, nor how much I played of robin hood: legend of sherwood, but those games also might have similar amounts of time poured into them.
I have more games on steam that have too much time put into them: FTL (176), supreme commander: forged alliance (120), geometry wars 3 (115), magicka (114), xcom 2 (101) hours. Steam also claims I have played 280 hours of counterstrike but I cannot remember playing more than one or two matches before deciding that it wasn't for me.
And the weird part is, though I like all these games very much, I have games that I have played a lot less, 5-15 hours maybe, that I aldo look on very fondly.