Update: I was unfortunately not aware of Shamus Young's severe criticism of Fallout 3 available here to link in the original piece and I regret that. It dovetails rather nicely with what I've written and it's much better executed than my piece. I strongly recommend anyone...
I think this is even better than Marvel vs. Capcom 2! This game has a huge character roster filled up with character from the Street Fighter world and character from the King of Fighters world.
The gameplay is where this game shines! With it's tag-team feature (you can pick 3 characters per team) and it's balanced difficulty. I don't really know what's the point of grooves that much so I usually pick the first one and it's the one I feel the most confortable with. Ultimate Rugal and Shin Akuma are a bit cheap but pick your best team and then you could beat them and unlock them as playable characters afterwards as a reward! Too bad their life goes down quickly though. The music is nice and really goes along with every stage and it's simply nice to listen to. The graphics here are quite possibly the best graphics ever in a 2D fighting game!
If you're a fighting game fan then you'll be playing this one for a long time. I really reccomend this great game.