Routh added that while he enjoyed sparring verbally with "Batman" star Bale recently at the MTV Movie Awards, he'd prefer to see the two heroes work together. "I don't think we should go toe-to-toe, unless one of us is deranged somehow by some mind-altering drug," he laughed. "We shouldn't be fighting each other; we should be combining forces." Singer said he'd consider directing a "Batman vs. Superman" flick, but only after the Man of Steel establishes his identity a bit more thoroughly. "I've thought about it for a long time — even a longer time ago, actually," the director revealed. "But I don't know who would be the villain. I guess Batman would be the villain, but then he can't be too bad, because he is Batman. So not quite yet. ... I think Superman needs to have his own movies for a little while before that happens." Either way, Singer insisted that "everybody's excited to do more ... and I'm sure we'll do another one." And Routh had this word of warning for Bale: "I don't think Batman really, really wants to go and mess with Superman." ...
And for those stating "Batman isn't a villain!" If Batman and Superman were to fight- yeah, Batman would probably be seen as a villain. As said before, remind me if I'm wrong- but Superman and Batman aren't the best of friends, but rather have a very complicated relationship due to their own moral code and personal beliefs.
Ok, maybe 'killing' was a bit too extreme. But, I have seen them duke it out before- due to their differing moral code.
I've read some of the World's Finest comics and own the Batman/Superman (animated) movie. Thus, I remember their moral codes causing a conflict that they overcome.