The main theme is just the most incredible piece of music ever - from the beginning right up until the ending. The love theme is amazing too.
OK, I didn't say that
Overall, I think Star wars is the better score (yeah, I know, shame Holst got there first). But I have never cared for the main title very much, it sounds jerky and awkward to me. Whereas, I think the Superman March is probably his best main title march, better than Raiders as well. But I don't think the Superman Love Theme holds up to Leia's Theme though and the Imperial March is classic.
Sorry to spoil it for you guys, but Star Wars is far superior to Superman.
Without commenting on the Korngold reference (as I've never heard it), I must say that Superman to me has always sounded like a comparatively cheap rip off of Star Wars. The similarity of the main theme is obvious, but Star Wars is the better (it also predates Superman). That being said, the main fanfare to Superman is not bad at all. It just pales in comparison to Star Wars.