Revealing mistake: Superman has just saved Jimmy at the dam and is holding him in the air. Jimmy's fringe is standing up thanks to some hair fixer to achieve the effect of wind blowing (though it's a green screen effect). When Superman sets him on the floor his hair remains up giving away the trick, until the angle changes and it looks all combed and nice.
Revealing mistake: When Superman takes Otis and Luthor to the prison wires holding them are visible.
Revealing mistake: When Superman leaves the prison, wires holding him are visible.
Revealing mistake: When Superman lands the burglar, wires holding him are visible for a brief moment.
Revealing mistake: Under Grand Central, the train that passes by Otis is the same one (5048) that kills the cop.
Revealing mistake: In Grand Central Station, the same extras appear in every scene, no matter where in time or place occurs.
Revealing mistake: After Superman saves the cat, he takes off and wires holding him are visible.
Revealing mistake: Before the Hoover Dam breaks, the places where all the cracks and water will later appear are easily traced on the concrete, covered in plaster and painted. Either that, or the real Hoover Dam has burst many many times and always through the same spots.
Answer: Just to clarify: Superman didn't spin the Earth backwards. We just see the world turning backwards when he went back in time. Of course this doesn't answer your question and it shows how difficult it is to write a good time travel story that doesn't leave the audience thinking of better ways to solve problems.
I guess the way they wrote it, Superman got to be the hero and also get the girl, not really too bad of an outcome.
briggs