Loved this movie, and Christopher Reeve, who became a real life superhero after his tragic accident. It will always be a huge what if in Hollywood had he not become paralyzed, seeing where his career would have taken him. I read his autobiography Still Me, where he talks about having Robin Williams in his class at Julliard.
Superman The Movie is one of the first movies I remember watching, and it's a film that's stuck with me ever since. I actually think the ending is perfect, and one of my favorite endings in a movie, because Supes goes against his father to become his own man, while saving the women he loves. It's properly set-up in the beginning where he says of his earth father's death, "All those things I can do, all those powers, and I couldn't even save him." It really puts into perspective how much Superman/Kal-El really cares about people and saving them.
To add to that, Reeve defined Superman in an interview as "a friend," which of course, he says in the movie after rescuing Lois. So, you combine those two elements, and that's really what makes Superman as a character and as a movie work. He's a god who isn't trying to relate to humans, he DOES relate, because he's suffered loss and overcome. It's his values that make him super, not his powers. It's why Lois calls him "a super man..." which prompts her to come up with his name (always loved that touch). Otherwise, you'd have the nightmare scenario of Homelander. And sadly, it's not something they were able to capture in Returns or in Man of Steel. The former tried too hard to copy the Donner version. The latter is largely junk. Snyder's Superman is cold and callous and "owes us nothing." B.S. Superman may fly above us, but he doesn't think he's above us.