The game that I cannot stop playing is Civilization V. I think it is partially because the game is turned based, so I just keep playing turn after turn, not thinking that one turn will take up so much time. I end up playing for eight hours straight sometimes. It is borderline unhealthy, as I have not moved from my chair since lunchtime. However, the game is also extremely replayable, as you are pitted against a different leader everything single time. Plus, sometimes I play with friends, and that is also super fun, and takes it even more time as humans cannot process turns as fast as computers. Despite the fact that it has nearly sucked all of my time, I still recommend Civilization V to anybody. You should totally check it out.