See, I think Joe Chill is a bad idea. The Wayne murderer should be nameless and faceless, as Batman sees (subconciously at least) each criminal he fights and brings in as his parents' killer. That said, in the context of the 1989 film, Jack Napier being their murderer works. Not only does it make everything very theatrical, and establishes Batman's personal vendetta against the Joker that couldn't be developed in a 2 hour film the way it could in 50 years of comics. For that instance and that instance only, I think it was a good creative change. But what do I know, I'm one of the few people who likes "Batman" better than "Batman Begins."