Hm...
I'll start with the bad points.
You fight scene was too Dragonball Z-ish. That gets minus points for originalality, not to mention that it lacked the dynamic action that a fight scene needs, it was a few punches and fireballs with some pointless running on the side. You focused too much on the effects of the fight for the fight itself to be good. I advise much work on that.
You don't seem to have alot for the scene select, not a good thing. And the Sonic-Mario crossover has been done waaaay too many times. I'm not saying you an Earthworm jock, I'm just saying that its been done before, alot.
For the good points.
I enjoy the recoloring of the sprites and the somewhat comical nature of the protagonist. I also liked the rpg music playing during the fight, although I can't pinpoint where I've heard it. Either Grandia or a Final Fantasy game...
Your concept has some originality, and killing Mario off is something I wouldn't have expected. No one ever kills Mario off. You get points for that.
All and all. Good job, work on the fight scenes and overall animation and you got yourself a great job.
3/5
6/10