Whereas superman is our savior batman is our society's need to see justice done at any cost. Because Batman will do what it takes to see the bad guys pay his characterization has room for flaws - knowing that he is always putting his finite life in peril makes him a solitary symbol for both righteousness and fear. Because, unlike our dark hero we din want to become him - we need him to serve up justice in a way that our penal system isn't designed for. They're totally great characters that emulate our two sides - we all seem to have a dark and a light side. all in all a very interesting discussion could be had.