All Superman would have to do would be to fry Batman to a pile of ashes from many miles away with his heat-vision.
I think the basic premise of the film is ridiculous, if not idiotic, in any case the average person in the street (who way outnumbers diehard Iron Age comic fans) - and they are the ones who would determine the success or failure of such a film - would surely view Superman and Batman as friends, not enemies.
That is exactly the reaction I get when I have people who come in the store and breeze through our graphic novel section. "Why is Batman beating Superman, that makes no sense. Why are they fighting? Is one of them under mind control? ." ..and I'm thinking to myself "In the sense that the writer and editorial is like a nasty supervillan force controling them, yes."
Frankly while I can appreciate the occasional classic Marvel hero brawl that comes out of some misunderstanding, I have never understood the comicbook fans desire to want to see two great heroes be nasty to each other or try to kill each other. ..and now entire gigantic and swollen crossover events are built upon the very basis of the writers magically forgetting the nobility of these characters and having them act like jerks.
Now *some* friction is understandable at the outset because if they are meeting for the first time they don't actually know each other. At the same time, neither of them are stupid. They would both get the hell over themselves and realize that together they are indeed the Worlds Finest team.