Continuity mistake: At the police station, the counter swaps from being stacked with papers to semi empty when the angle changes.
Continuity mistake: When Jimmy is rescued by Clark in the Hoover Dam, Jimmy's hair during the flight is way longer than when he was hanging.
Continuity mistake: During the first scene inside Perry's office there's a radio on the background resting on a white book and a fat red volume. The white book changes positions depending on the angle.
Revealing mistake: After saving Jimmy from falling to the dam, during the flying sequence a couple of wires are seen between them.
Continuity mistake: When Lois's car first runs out of gas, the car radio is running. When Superman comes back after turning back time, the radio is off.
Continuity mistake: When the young soldier is about to reanimate Ms. Teschmaker his helmet is behind her arm. When the Captain lifts him up the helmet appears one meter away from the arm.
Continuity mistake: Jor-El teaches about Einstein during Kal-El's voyage to Earth, but when Superman talks with him in the Fortress, Jor-El says "I will have been dead for many thousands of YOUR years".
Other mistake: In the extended version, there is a scene where the people are watching the news about Superman saving the chopper. The TV shows footage from below and from the other side of the building - no one could take that shot.
Other mistake: At the time when Lois is on the train and sees Clark running alongside, she is about 8-10 years old. About 12 years later she is 30.
Continuity mistake: The blanket used by baby Kal El to get to earth is red, blue and gold. When he lands it's just red.
Continuity mistake: Superman's hands' position when holding the fuselage of the plane swap between shots.
Continuity mistake: When young Clark is running next to a train, he passes by a pole on the ground. Half a second later the angle changes and he is inches away from the pole, which he passes by again.
Continuity mistake: When Superman and Lois are being mugged in the alley, watch Clark's tie before and after entering; there's a thick blue coloured stripe near the knot, which later disappears.
Revealing mistake: In the extended version, when Luthor fires snow at Superman, the icicles bounce, rather than shatter, revealing they are some type of foam or plastic balls.
Continuity mistake: When Krypton is exploding, Superman's mother looses her balance and falls backwards. In a new angle a frame later she is up-straight loosing balance again.
Revealing mistake: When in the prison yard, Luthor's bald cap is hanging loose around his nape.
Continuity mistake: The first shot of Lois' red car shows it clean and shiny, a second later it's all dusty and dirty.
Continuity mistake: When Luthor smashes the green car, its wreckage is different in the shot when the soldiers arrive: The hood is open wider and the windows are broken.
Continuity mistake: During the trial, Zod and Ursa swap places in a couple of brief shots.
Continuity mistake: At the end of the football game, a guy with a cap tells Clark to have the clothes ready. But his lips are not in synch.
Answer: Superman has chosen to use his powers on Earth for the good of mankind. It would seem that lying to them would be an unneccessary thing to do, so it appears to be a personal choice. Interesting trivia: the closest he comes to lying is when he tells Lex Luthor to get Zod and company into the molecule chamber in the second film. Listen closely, he only says that it is a molecule chamber that takes away their powers, he never actually says that being inside will make them lose them, only that he wants Luthor to get them to go into it.
Jazetopher
That may be the closest "Superman" comes to lying, but Clark Kent does appear to lie. After the mugging scene in the first movie, Clark tells Lois the contents of her purse, and when asked how he knew (obviously from his X-ray vision), he says "wild guess" which was a lie.
jimba
Not only that but, he spent his whole life pretending to be ordinary so, in fact, he spent his whole life living a lie.