Well first I will say the game is awesome but there are always things they could improve upon....
1. much much better online play. rankings of people, characters, etc. No lag time. No friend codes. Ability to speak to each other with wii speak. lots of stuff for the online mode.
2. For the game mode, i would suggest less zoom outs and options to set zoom setttings and maybe even an option to try a split screen. I hate when the characters are so small I cant even see whats going on and it never feels like they are as big as say the online practice stage.
3. add new characters...but really they have plenty but more is always better...like mega man
4. items - sometimes so much is happening you cannot tell what is happening and i dont think you can set that in the online mode