Can't say I expected this one. On the verge of losing their WWE license, THQ appears to have a back-up plan. May's NPD sales numbers indicate that "UFC 2009 Undisputed" sold nearly 680,000 units, grabbing the top spot for the month and just about doubling Wii Fit, which sits at #2 with 352,000.
Is this the dawn of a new fight age? EA seems to think so, as they've already announced the development of their own MMA franchise, (titled "MMA," natch), which is coming next year.
You can check out the rest of the sales numbers at GameSpy.