Hard to say, but I think Black & White 2 might be the worst game I own.
I just thought of another bad game, Sim City 3000. The building graphics take ages to load, even on modern computers. But I don't think it's as bad as Black & White 2.
Strange but I liked Iron Storm and actually went out and bought it. Also Black and White 2 was not bad even though it took a lot of time figuring out what was going wrong and beating one mission, overall it's a great and complex strategy game.