Superman is notoriously hard to write a movie around. In comics they can have him fight beings of supreme power (darkseid, doomsday, gog) but puting that level of conflict in a movie is really hard.
If you look online the the takes on superman 5 were horrible. Kevin Smith wrote a treatment that was supposed to be pretty good. He talked about it in the "Evening with Kevin Smith" DVD.
My $.02: I liked the movie. It was a lot like the first Superman movie but I don't really think that it would have been possible to do much better this long since the first movies
(The best part was when Nuclear Man escapes from the reactor and killed Lois Lane )
Fleche!! Fleche for fantasy.
"Dude! Zombie Keith Moon would be an unstoppable force!!