Creating Characters With Stan Lee
GameDailyBiz has an interview with Stan Lee that touches on a talk he gave at the 2005 D.I.C.E. Summit entitled "Superheroes - Creating Characters for the Ages". From the article: "I submitted the idea of Spider-Man to my publisher and he hated it. I said my hero was a teenager -- the publisher said a teenager could not be a hero but only be a sidekick. I said he was insecure and had personal problems -- my publisher said a hero does not have personal problems... The lesson to be learned, don't listen to experts because they don't know what they're talking about and just get you down."
Pluvius is right though. When Batman first came out in the 40's, his character was very dark and almost pulp-like. He killed bad guys on a regular basis. But when he got popular during the Golden Age, he was definitely the "Adam West" style Batman, who's biggest non-Batman-related concern was whether to go to the Charity Bachelor Auction or not. We still were told why he became Batman of course, but the comics were all about his actions as Batman, and any story we saw as Bruce Wayne was just peripheral.
It wasn't until Marvel came along and started writing characters who had problems in their non-hero lives that you started to see things like Batman going dark again.