There are some movies that are bad because of offensive content. Some movies are simply unwatchable because they are filled with the obscene, scatological, pornographic, or offensive. Superman 4: The Quest for Peace has none of these problems. It has nothing that is obnoxious in that manner. And yet it manages to be the worst movie I have ever seen. It may well be the worst movie that you could possibly make that did not include such things.
The movie was not the 'this is boring, just turn it off' kind of bad. It was the 'Golden Turkey' kind of bad, where you cannot stop watching because you cannot believe just how horribly bad it is, and you wonder if the spectacle of awfulness can possibly continue at this rate. This movie is amazingly bad in part because it always finds new and inventive ways to get worse. There will be at least half a dozen points in the movie when you think 'It cannot possibly get any worse than this' and then it does.
My friends warned me about this, before they had me watch the movie. We watched the movie specifically to gaze in awe upon its train-wreck horror. They told me that it would be the worst movie I ever saw. It did not disappoint. In some ways, It provided more entertainment value than most good movies.
Superman 4 is such an inept superhero movie that it makes the worst episode of the 1960's Batman TV show look like Batman Begins. It is so horribly cheesy and cartoony that it makes Dragonball Z look like Saving Private Ryan. It is, and I did not think this would be possible, worse than SciFi channel original movies.
Most of the horror came from the fact that I have never seen anything that showed such amazing disregard for the laws of science. The people who produced this showed a hitherto unimaginable ignorance of the basic facts of physics, chemistry, and thermodynamics. The list of crimes against science starts with Superman's cape billowing in the hard vaccuum of outer space, and then gets worse and worse.
The disregard for a sensible plot and for characters that do things for a reason is just as bad. Things simply happen at random for no reason.
All of these things could be excused, at least partially, if the film was obviously intended to deliver mindless fun action sequences a la Michael Bay. It is not. The true horror is that it is really trying to take itself seriously, and be counted aside films like Mr. Smith Goes to Washington as a tale of how an individual can improve the world. It is infested with sad, pitiful, clumsy attempts to generate Image and Message.
Some of the problems in this film are, unfortunately, endemic to Superman films in general. They work very hard to portray Kal-El as some kind of messianic savior of mankind, a god walking among men who will save us from our own follies and sin. The title character ceases to be a character and instead becomes something to be worshiped rather than identified with.
I could describe in detail some of the scenes that make it bad, but that would take far too much time and would spoil the movie for those who have not seen it. If you have the chance, see the movie with a group of people, and be prepared to react in slack-jawed horror at the awfulness of it.