Depends on your budget, I would go for the Intel Core 2 Duo E6400 or E6300 though. Core 2 Duo's blow away AMD in terms of performance right now, so Intel would probably be your best best for gaming. If you can't afford either of those, then go for something like the AMD Athlon 64 X2 3800+.
E6400 http://www.newegg.com/Product/Product.asp?Item=N82E16819115004