Needs some work
You could make a good flash out of this, but you need to work harder and longer on it. For instance, spend some time animating the sprites instead of just rotating them around. It really needed sound effects, too, and it would have looked nicer if it was zoomed in a bit. Work hard and keep trying, though.
okay then
ok im gunna be honest that looked justlike you took a picture and used a motion and finished it in 12 minutes please just try better
um....
im sorry but this.... this sucks...im giving you a 3 because i like the music and luigi won... but seriously why not try harder....
Hilariously bad
First off, improve the graphics. Add a background and improve the animation. Most of this is just the Mario Bros. being tweened into each other in Purgatory.
Second, compress the audio because it would take less time to load and takes up less space. I've seen longer and more animate sprite animations with much lower file sizes.
Third, have a good reason why they fight other than video game characters battling for the sake of video game characters battling.
Fourth, read tutorials and carefully examine some of the better sprite movies if you plan on making something else like this.
Oh, and the zooming at the end is priceless XD
Not all that great
This flash was just lacking majorly. The background being all white was the major issue, having an all white background like that is usually quite jarring to the eyes. The flash was also kinda boring, because we've seen Mario vs. Luigi fights hundreds of times on the net. Bring something new and original! You have some potential, but try some new material, as well as bigger sprites.