Re: Greatest Composer of a Batman Film!?
Personally, I think Walker and Elfman shared similar influences, more than Walker being specifically influenced by Elfman's BATMAN scores. Listen to Bernard Hermann's score for VERTIGO, then watch BATMAN, BATMAN RETURNS and BATMAN: THE ANIMATED SERIES. You can hear the Hermannic touches pervading through all of those in different ways.
Also, shouldn't Nelson Riddle be an option here? His score for BATMAN: THE MOVIE is fantastic. I'd probably put it just behind Elfman and Walker.