Regarding Superman's vision: To each his own taste, I suppose, but I think any counterfactual assumptions in a science-fiction or fantasy story (such as Superman's special powers) should be defined early in the story, and then the rest of the story should be consistent with those assumptions.

I'm not saying X-ray vision couldn't be a metaphor for some more complicated power, but if it is, we need to have the storyteller give us some sort of explanation of how it works. We shouldn't have to invent explanations ad hoc.

(By the way, I never thought Superman's eyes emitted X-rays. I only thought he could see them when they were emitted by some other source, such as the sun.)

The audience will feel cheated if, at the climax of the plot, Superman uses some power we didn't know he had.

Actually, I did feel cheated when Superman reversed time by flying rapidly around the earth. Who knew he could do that? And how the hell would it work? I was so disgusted I never watched another Superman movie.

See Deus ex machina at Wikipedia.