Much like the Zack Snyder cut of Justice League (2017), Superman II is famous for having two cuts. During the production of Superman: The Movie (1978), conflicts arose between Richard Donner and The Salkinds. They accused him of going over budget and being behind schedule. Donner fired back, saying he wasn't given a budget or a deadline. After the success of Superman: The Movie (1978), the Salkinds decided to fire Donner and remove Marlon Brando's scenes from the theatrical cut of Superman II (1980). Richard Lester was brought in to finish the production of Superman II (1980). In order to receive full directing credit, Lester had to direct at least 50% of the film.
The plot of both cuts is pretty much the same, with some different scenes. For example, Lois Lane (Margot Kidder) tests Clark Kent (Christopher Reeve) in the very first scene. Lois finds out who Clark Kent is by shooting him with a blank. That was test footage because Donner couldn't reshoot the scene. Most importantly, the re-inclusion of Marlon Brando as Jor-El, who was replaced by Lara (Susannah York) in the theatrical cut. Donner and WB's biggest concern for the project was getting Brando's estate's permission to reuse his scenes, similar to Superman Returns (2006). Donner said that if they couldn't get permission, there was no point in doing the project. This cut also features John Williams' music. However, there is nothing new here; it's primarily taken from Superman I. Donner first phoned Williams to see if he was available to compose completely new music, but he was preoccupied with scoring for Revenge of the Sith. Finally, all of Lester's slapstick humor and newly filmed scenes were removed. Donner didn't want to use any of Lester's footage because it hurt him.
Out of the two cuts, I like this one better. The moments starring Lois Lane and Clark Kent, the addition of all of Marlon Brando's deleted scenes, the closure of some plot holes, and the overall faster pacing are just a few of the many areas where it excels. This cut makes more sense to me and stays true to Donner's original vision. Either way, both cuts are excellent; I simply prefer this one, as I mentioned.
I know most people prefer the theatrical cut of Superman II (1980), which I understand, but most fans agree that Marlon Brando as Jor-El shouldn't have been cut out of the film. All the fan edits I've seen of Superman II feature most of the footage from the theatrical cut but also include Brando's scenes. That, in my opinion, is a true fan edit. Although, I hate that memory wipe kiss. It's very dumb.