On a non-Animated series note, I believe that the biggest mistake(s) made in a Batman film (and this was done in the two greatest Batman films) was to reveal the identity of Bruce Wayne's parents' killer. Both times it worked great for the one film (although Begins probably could have done without it), but at the end of the day, it gave Batman direct retribution for the act that in all other media (especially the comics) haunted him and motivated him his entire life (thus meaning Batman needs a different, perhaps too noble motive to his actions in each successive film). The drive that Batman has to do what he does stems from the fact that anyone could have killed his parents; that so long as crime exists, more Martha and Thomas Waynes will die on the streets.

On another note, has anyone noticed that the name John Corben was given to the Waynes' killer in Begins? Anyone recognise this as being the same name as Superman's nemesis, Metallo (the suspicion that John Corben/Metallo killed Batman's parents was brought up in Superman/Batman: Public Enemies not too long ago)?