its been done...
i'm not saying its stolen (cuz it isnt), but the whole "mario vs. sonic" scenario has been done so many times its gotten old and unoriginal (to me at least).
the idea of adding new fighters as the story progresses makes it a bit unique from the others, but not by much.
also, 2 craters just appeared out of nowhere when sonic and mario jumped up high. i suggest adding some smoke or something similiar to hide their sudden appearence.
overall a 7/10 from me. good work animating, but there's still some room for improvement (like hiding sudden changes for example).