It is really quite difficult to work out, but it is probably sports games on their own, just because of FIFA....
But neglecting FIFA, since it isn't a proper game, Steam says my most played games are:
Empire Total War 144 hours
Football Manager 2010 86 hours
Cities in Motion 60 hours
Total War Shogun 2 56 hours
Napoleon Total War 36 hours
So adding in well over 100 hours on Halo Wars, strategy is probably my most player genre. RPGs probably takes the runner up with at least 150 hours on Mass Effect, with hundreds on Final Fantasy games as well. (Oh and Deux Ex, Dragon Age Origins, Witcher 2, Fallout 3, Skyrim and more)
I guess shooter is third, with 100 on CoDs, more than that again on Gears, plus 75+ on Uncharted as well as countless other games (80 hours on GTA if that counts)
So basically, I have played a lot a lot of games... But shooters, RPGs and Strategy are probably the main genres (though I guess it depends on what you count as action games not shooters and then we open a whole new issue...)







