Well I think that gaming standards has been raised a lot.
I have UFC Throwdown, UFC Tapout 2, Pride FC, UFC Sudden Impact, K-1 Premium Dynamite. Best would be Pride FC or one of the K-1 games. The newer K-1 games are Japanese though so you may not be able to play them. The UFC games arn't that bad but you may get bored.. The best one to get would be Pride FC because it has a pretty decent roster aswell as a very good Create a fighter mode.