It's depressing to think, but there could have been a great movie in Superman II. Yet, due to typical studio politics of the 70s, we are given this movie instead. It's even harder to believe anyone would find Marlon Brando's work unworthy of any movie. Donner really deserves the credit for 70% of what works in the film, while Lester deserves the 30% that doesn't. So on the basis of Donner's work I still recommend it.
After seeing the Richard Donner cut.. In all honesty, Donner shot this poorly from the outset. Superman, a COMEDY. Really.. Well, in that case, it makes sense to bring in a comedy director to save the production. Enter Richard Lester. I don't blame Mario Puzo. Something very transgressive and interesting could have been wrung from this script.