We used to live on "Earth Prime," but that Earth along with most of the others was destroyed during the Crisis on Infinite Earths. Then it was revealed that the post-Crisis Earth is slightly larger than the Marvel Earth, accounting for the extra cities like Metropolis, Gotham, etc. We obviously don't live on the Marvel Earth, but I think we, too, live on a smaller Earth. Since the appearance of a Superman seems to be linked to the existence of Metropolis, and our Earth is too small to host a Metropolis, there's almost no way any incarnation of Superman could exist here.

Unless this is a version of Earth Prime that wasn't destroyed in the Crisis (different timeline, you know), in which case somewhere there's an Earth Prime Superman ... but he's as bad as Anakin; the one from the Crisis Multiverse recently tried to destroy the DC Universe and went on a whiny rampage. (Another reason I don't read the monthly books.)

Our best bet for getting these two together is a reconceptualization ... we must model them in a computer. Perhaps we can distribute the computation load over a number of systems, like SETI@home does. It's certainly just as important.

As for lightsabers ... I kind of doubt they'd even scratch him. Even if they did, he still has super speed to react and fly away from danger. And it's unlikely that kryptonite would be used in constructing a lightsaber, seeing as kryptonite is, you know, only found in the remains of the planet Krypton.