I also play Civilisation IV but I'm getting a bit bored of it at the moment. Currently I'm playing a game called Titan Quest which is excellent, kind of a chop-and-slash sort of game and quite repetitive but a lot of fun nonetheless. It's not for everyone but I recommend it.
I also play Oblivion but my PC specs are a tad weak to play it to the max. I'm thinking of upgrading in about six months time though.