Looks like Tatsunoko Vs. Capcom is shaping up to be the definitive non-Brawl fighting game for Wii, if Joystiq's review is anything to go by.
http://www.joystiq.com/2010/01/25/review-tatsunoko-vs-capcom/
Some notable quotes:
"Looking at its roster and the fact that it's on the Wii, it would be easy to dismiss Tatsunoko vs. Capcom as a gimmicky fighting game, but it's an honest-to-goodness hardcore entry that is among the very best Capcom has made in recent years. It's easy to get into, yet surprisingly deep and steeped in fan service. It's also one of the nicest looking games (so far) on Nintendo's console."
"If you've been following this game since its announcement as I was, you're going to be very, very happy; it's everything I could have asked for, and a real standout on Wii."
Oh yeah, checking this game out for sure now.
