I guess Counter-Strike: Source - Over 800 Hours since it was released in 2004.
Pro Evolution Soccer and NHL '95 are the games i play most at the moment.
I also have my traditions of playing Jagged Alliance 2, Monkey Island 2, Indiana Jones and the Fate of Atlantis and Star Trek - 25th Anniversary at
least once every year.
Not to forget some Sega Mega Drive Classics like Streets of Rage 2, Golden Axe 2, Two Crude Dudes and World of Illusion, nowadays mostly online with
Friends. I don't even know how many times i have killed Dark Guld now....must be in the triple digits already
And every year at New Years Eve we have the big King of Fighters '98 Tournament