Batman is one of those characters I think of as having gone through the imaginary mill and come out a very different character at the end. Yet he's been that way so long now, many see this as the definitive Batman and can't see how it subverts the previous status quo.
When I read Frank Miller's DARK KNIGHT back in the 1980s it put me in mind of a MAD magazine parody. I think Miller was deliberately trying to push everyone's buttons by doing a take that tipped over all the sacred cows. He was just having a laugh, but it seems like a lot of people took it seriously and began to change Bruce to fit that model. So nobody appreciates that the DARK KNIGHT is meant to undermine everything the Caped Crusader stands for.
Sure there were certain dark aspects to Batman in his first eleven issues of DETECTIVE COMICS, but even in that short run they were transitioning away from the grimmer aspects of the character toward something sunnier. And once Jerry Robinson became Bob Kane's inker, he gave Batman and Robin those toothy smiles that defined the Dynamic Duo into the 1960s. Even Neal Adams paid homage to that Robinson smile in his cover for BATMAN 200 (March 1968).