ask yourself this question...
I fyou could have any super power at all, what would it be? Most answers would be one of the powers of superman....flying, x-ray vision, incredible strength....
what does batman have? A utility belt with a lot of cool bat-gadgets, but no powers of his own.
Sure Superman has that kryptonite weakness, but Batman has a weakness for beautiful women, and last time I checked I could find a hundred beautiful women a whole lot easier than I could find an ounce of kryptonite.