Yeah, that was pretty awesome! It did also serve to provude new comic ideas
I know Frank Miller was really impressed by Baldwin's performance since it was based in part on Batman: Year One. Baldwin took the whole idea of clueless playboy by day, vigilante by night and ran with it. So when Miller continued his Batman stories after 1989, it was clearly influenced by Baldwin.
So if Keaton (the runner up) had been cast, Miller's later Batman comics might have suffered.