The Donner score is great, but don't fool yourselves into thinking it's a necessity for a new superhero movie. The Bruce Timm cartoons (both the animated series and the Doomsday DVD movie) had two separate, but heroic and powerful themes that fit Superman perfectly.
The Nolan movies showed that yes, you can come up with a new theme for the hero even if an older theme is established. The music in Batman Begins better captured the rage of Nolan's Batman better than the Elfman music too.
As for the origin, I am against skipping over it on the belief that "everyone knows it already." No, not everyone does. For a generation of kids, this movie will be their FIRST exposure to the character. It's 2008 now, even the Bruce Timm animated series from the late 90s is before the time of kids these days. Even if people are familiar with Superman, starting from the beginning allows them to jump on and feel like they're a part of things.
IMO, the worst mistake Singer made, worse than goofy Lex, no punching, or superkid was skipping the origin. Imagine being a 5 year old watching Superman Returns for the first time...and it starts with text telling you that you've already missed the character's greatest adventures. WTF is that? Don't make the same mistake that Singer did.