Good, could be better
I'll break it down into parts:
Graphics and Style: Could have been better. Even retro can be polished. Specifically, things like dust clouds coming up from the ground when Megaman bounces really add to the feel. That mega blast was a bit plain for a flash animation. Also, few people get this perfect and you're not one of them but the timing is key. Things like Megaman drifting in the air or some actions happening just a tad too slow (even if it's a fraction of a second difference) loses that edge.
Sound : Was ok. The good part was that I didn't hear people blowing on the microphone like in other submissions. The bad you may not be able to help but the voice actors could have been more suited to the characters. Oh, and I recognized the Cave Story tunes. Funny. Great game, that one.
Violence: Appropriate.
Interactivity: Could have used forward and back movie jump buttons. All movies should have these. Or at least a scene select.
Humor: Again, appropriate.
I hope you take the criticism as positive feedback, as it was intended. Good job otherwise. Spend a little more time tweaking and polishing things and your next animation should be great.