So Rat and I decided it'd be fun if we started up a succession game, sort of like in the other topic, only this time, it'd be Civilization 4. For those not in the know, a succession game is a shared playthrough of a game. One player would start play, keep a log of what they did, and then pass the save file onto the next player, who would continue. Obviously, this creates a different sort of gaming experience than simply playing the game normally would.
Civilization 4 is one of many games that can be played this way, and one of the games I know many of us actually have.
No expansions are necessary. Those of us with expansions will just have to play the bare version.