The Sims 3 Hounestly, I hate this game, because EA never gets it to work right on macs. Do they do any quality assurance? At any rate though I remembered when I played the sims and it worked and it was very addicting. Endless things to do. Give me the sims with expansion packs and I could definitely put this on the list.
Team Fortress 2 Another game that doesn't have an end to it, I feel like only games such as these can be long-lasting and be a good choice for a list like this.
Dragon Age Origins or Dragon Age 2 These games have huge replay value. I could spend a very long time going through every possible outcome and trying out the romances with everybody. It goes on the list.