By far its Resogun, I must have replayed it around 50x already and I still want to get to the top 10 world records. The most addictive game ever created, sometimes I wish I never discovered that game as it takes so much of my time.
But if we are talking mainstream single player games, that will be the very first tomb raider, finished it around 20x, not because it was a great game, but because back then games were shorter and also because I was a kid with no money to buy games so I was stuck on the same game for months until I could afford another.
If we talking games from the past 20 years, I'd say Halo, Alan Wake, The Darkness or Max Payne 3, I've played each at least 5x







