Barring Krytponite on Luke's part, no way Superman gets beat. Luke has: telekinesis, lightsaber mastery and limited levitation. I'm thinking Superman is impervious to lightsabers, and Force-based telekinesis seems to have (relatively modest) limits. So I doubt, for instance, that Luke (or even Yoda) could just rip Superman's arms off using The Force. Superman could fry Luke w/ his eye-rays before Luke even got close enough to use the lightsaber in the first place.