Smeags on 06 April 2010
556 Hours with Super Smash Bros. Brawl (That's 23 days straight... blech.)
267 Hours with Pokemon Diamond (Close! 
)
223 Hours with Animal Crossing: City Folk (Another close one...)
Ones I know that are over 300 hours are Super Smash Bros. Melee, WarCraft III, StarCraft, and TimeSplitters 2/Future Perfect.
That's all I can think of off the top of my head...
