Ageless Game
It's hard to imagine this being considered an "old game" now, but Civ 5 is, but it doesn't really show it's age outside of graphics that aren't entirely impressive. However, what's there is tons of hours of strategy and ways to play with the various leaders and empires, all within the nice neat package (on sale). It's really hard to go wrong with Civ 5 because I think the AI puts up a fair challenge, and pretty much any computer can run it.