one game to play

[ThreeName]

Probably Civ V, it has the most pure replay value out of all of my games.

 

[Atlys]

Probably Oblivion, seeing as it is my favorite game of all time. I've probably put more time into it than most MMOs I have played and I still haven't done everything it has to offer. Plus it has mods. I could spend some of my time coding Oblivion multiplayer. I drool just thinking about it.