Oh, come on, there is no way he could have the ability to leap entire buildings just because he's from another planet. First off, since he's pretty human in shape, that restricts just how heavy his world could have been - 2 gs would be pushing it for local gravity....
What if people on Krypton are also denser, hence having more dense muscle and bone tissue?
I think the original inspiration for Superman's leaping ability was also comparison with the leg strength of insects, one of the themes in the John Carter series. A human-sized insect could leap over a building. I'm pretty sure one of the earliest Superman stories draws that analogy.