Besides, Batman's all about
angst. His kind of angst, though, isn't about him moping in a barn over lost high-school love but about turning that angst into anger and action against the criminal element that causes
In The Dark Knight Bruce Wayne has just lost a life-long friend and a woman he loved deeply enough to give up a double-life for. Of course
he's going to cry and be a bit pouty but then he takes that and unleashes himself onto The Joker and sacrifices his own hero's character for the sake of a greater good.
Superman, on the other hand, is supposed to be pure anti-angst, someone who has had it trained and built out of him to be a beacon of pure virtue and heroism. In Smallville, Clark/Superman still hasn't gotten over the girl who tried to marry his mortal enemy.