I tend to jump around in games too much to put a huge amount in to any one game these days.
My most played on Steam is Skyrim with only 60 hours. NS2 is 2nd despite me only getting it last month, at 40. I have tonnes of games somewhere from 20-30, I tend to get bored at this point.
That obviously excludes MMOs, WoW was at about 250 days before I stopped playing...So many regrets. Battlefield 3 and Starcraft 2 probably top Skyrim as well.