Better than I expected...
3/5
That's a high 3, though. At first it seemed like your average Mario flash - a big fight scene with boring sound effects. And that's what it was until Bowser busted out his Super Mario World flying cup rendered in 8-bit graphics. That's when things got interesting. I liked how elements of the 16-bit world were simplified into 8-bit and the fight scenes became a little more interesting.
But there were still a lot of drawbacks. The sound effects were boring to listen to and very repetitive. And if you're gonna go for the violence, then go for it! It needed more blood and guts.
Otherwise everything was pretty good. The sprites were good and the animation was smooth. The music was passable, and the story was non-existent (but that's forgivable in this kind of animation). Keep up the good work.