Very Nice!
This is kinda wierd because a few days ago as a project I started in school I started remaking street fighter. LOL
I was using all the original sprites as you used in the beginning but it was really just for experimenting.
Anyway this was a pretty sick flash. Some improvements could be to use effects that flash has like blurs. Most top rated sprite animations use blur effects for really high speed movements which could be something else you could add in.
Other than that I thought it was great. Ryu seemed to be in control the whole time though. His hits sounded harder and it seemed like he got bigger combos.