Nice.
It's really impressive, the length you went to imitating the style of the animated series. The sound was too faint to be really effective, though, and some of the animation really broke the mood. It was very smooth and interesting in the beginning with the buildings, but the running movements of the cops and the crooks kind of ruined the illusion.
I'm sorry if people rate you badly because of the Joker's real origins or whatever. You'd figure there have been so many "reinventions" of the various superhero comic series that people wouldn't mind a few inconsistencies. (Ex: What do X-Men: Evolutions, X: Men the movie, and the X-Men animated series that aired in the 90's have to do with each other? Very little :P).
I was going to give you an 4, but after seeing the last poster give you a 0 for a reason that had nothing to do with your actual flash movie (not a word about the animation or ANYTHING!), 5.