also superman has the problem that he's a bit boring due to being unbeatably 'super'. a little personal anguish might add some interest.
As long as it doesn't change who and what Superman is, then fine. If it serves the story, then fine. But if it just "dark for the sake of dark", which is what alot of TV and movies have been for the last decade, then it's silly.
But, I'll reserve judgement on MAN OF STEEL until I actually see it.