Stemming from the discussion of Bruce's darkness, I think the inevitable questions comes to this:
Where would Bruce be today if his parents weren't killed?
Yes, I know it sounds like a bad AU fanfic, but I think it's the question the darkness discussion is really getting at.
For me, without that fateful event, I can't see Bruce truly becoming Batman. I see him as a philanthropist, much like his father is often depicted as. He uses his money and company to make Gotham a better place. I think the most invasive Bruce would be in this scenario is to become a well-meaning politician (if such a thing exists).
In short, without the death of his parents, I don't see Bruce ever developing the anger or drive that is the original spark that begins his journey to become Batman.