Definitely Age of Empires II: Age of Kings and its expansion The Conquerors... and they released an expansion last year, days are not long enough already!
I spent every other night for 5 years of the last decade on Konami's Winning Eleven 6. The other 5 were spent on Dynasty Warriors: Gundam 2. Both on the PS2.
I enjoyed 'Need for Speed: Most Wanted' in the past. I am currently playing Asphalt 8 downloaded from Windows Metro store. The multi-player section seems to be more interesting than the single-player's.
I spent 2000 hours playing Serious Sam HD: The Second Encounter Also a lot of time playing GTA and NFS series
I've been absolutely obsessed with Dark Souls and Dark Souls II lately. I'm better at DSII, but it's probably a little easier to play. I'm about finished with the NG+ on my latest character, though NG+ seems a lot easier than normal NG. Maybe it'll be harder on NG+2
Skyrim, always something new every time I load it. Thousands of hours on that thing. Short of that, unreal and unreal tournament since their conception lol