This thread really makes me want to re-activate my World of Warcraft account so I can check my /played on it. I really have no idea what it was when I quit. But I raided 4 nights a week from the beginning of Burning Crusade to the end of Cataclysm + arena + bgs + dailies + levelling alts. So... thousands of hours at least.
At least 500 hours in The Sims 2 (PC).
Team Fortress 2 - 227 hours.
Command & Conquer Red Alert 3 - 118 hours.
At least 100 hours in C&C: Tiberian Sun; SimCity 3000; LittleBigPlanet 2.
At least 80 hours in Wild ARMs 3.
Currently SSX (2012) must be catching up. I'm playing it for a couple of hours every night!