I'm not going to bother with a detailed review of these games. Mainly because I haven't beaten them death yet. But I'll say what I think with the time I've had on them.
MadWorld... what can I say? It's boring! Sure you get to kill a lot of people in fun creative ways but after doing it for an hour it gets very repeatitive and since there is no real story(at least not one worth paying attention to) you get tired of it fast. The graphics are not good and I feel the artsy black and white color pallete is designed to hide the fact that the graphics are weak. The play machanics are equally slugish and uninspired. I mean I really can't think of a reason to go back to this game and beat it.
Tatsunoko vs Capcom is better but not by much. When compared to other fighting games it lacks a lot. Maybe it's because I was raised during the salad days of Street Fighter II when your skill with 6 bottons made or broke you in combat but this 3 botton fighter just doesn't play well. I'm not saying it's not a fun game for beginners but when I select Ryu I expect to have 3 punches and 3 kicks not 3 random punches and kicks that I cannot control.
Tatsunoko vs Capcom does have some fun worthwhile features that I like. It has internet matches that set up fast and easy with other people playing around the world. It also has rankings and an ingame store where you can unlock characters and other special bonus material using points you get from playing the game. You can even get a rival online and strive to one day kick the shit out of him.
Out of all the games I have on the Wii I really like Tatsunoko vs Capcom and hope that they try bringing out a fuller version of the game with 6 attack bottons instead of 3. As for the sound, I'd give it an A. The voice was good the sound effects were good and the music was good. The graphics were ok. No where near the PS3 or 360 but good enough to look like arcade quality. The animation of the characters and their design was excellent and the list of fighters was pretty good though I would of liked to see more.
MadWorld I'd Flush it! Just because it doesn't have anything really to offer other than violence.
Tatsunoko vs Capcom I'd Buy it! if you don't have a PS3 or 360. If you have a better system then I'd rent it just to try out the anime characters.