I will say that there's a subtle difference between the high quality and the low quality versions, but the high quality version still has a few problems.

Anyway:

- Could use a loading screen particularly as the 5.8 mb filesize isn't desirable. I'll give you that it doesn't start until its loaded, but something saying loading could be good.
- The sounds sound terrible, really bad quality and echoing? Did you record them directly from MAME on a slow computer or something?
- Win counters on lifebars.
- The idea is interesting yet I don't see it ever being included in a game. But still, can't shoot ya down for that.
- Blood could have been better, at points it was particularly jumpy as 2 frames isn't enough in animation.
- There are areas of low quality surrounding the sprites.
- It seems to run a bit slow.

Still though, with those things fixed it could have been a pretty cool animation.
I rate it a 5.5/10 at the moment, but with all of the touch ups it could be a fair bit better.
EDIT: Another thing I'd recommend doing is placing the Flash file on an html page as viewing it in the browser can result in low quality (and becoming the size of the window) and also reduce it's speed.