Batman may be infinitely cooler than Superman but let's not kid around here, a Batman vs Superman fight isn't even a contest. Pound for pound, power for power, Superman would destroy Batman. So instead of making a full Batman vs Superman movie, they should just show the different ways Superman could kill Batman.
Like this video by Mr. Sunday Movies, only with a blockbuster budget. I'm pretty sure a movie of Superman beating up Ben Affleck over and over again would break a billion in the worldwide box office. Come to think of it, maybe that's why they got Ben Affleck to play Batman in the first place!
And here's five ways that Batman might be able to beat Superman (without Kryptonite):