Superman 3 was awful because the Salkinds decided to make it a Richard Pryor comedy and the script was rewritten on the fly to accommodate that.
Superman 4 was produced by the Cannon film group that was trying to grow from B movies into big budget fare in the mid-80's and was dropping tons of money into failing movies in 1985/1986 including paying Stallone $12 million dollars to appear in the arm wrestling movie Over the Top and dumping a bunch of money into the woeful Masters of the Universe movie. Superman 4 started filming with a script, scenes storyboarded out and planned for a $36 million budget for a 2 hour and 10 minute movie. However, Cannon group both went into bankruptcy and were under SEC investigation so the budget was cut to less than half down to $17 million DURING production requiring whole scenes to be cut after others were filmed, complete rewrites to use what had been filmed without the context of any of the scenes that were cut and almost no money to actually complete effects shots which now were done on the cheap or not at all. So you ended up with a chopped together movie that was 87 minutes long, made no sense, and where almost everything looked like crap.
I'm obsessed with the idea that in Superman 3, Supes finds the giant computer that's transforming people, says, "this is Brainiac?!" and then from behind him we hear, "No Kal-El." And Richard Pryor, with no emotion on his face, tosses off his hair to reveal the Braniac symbol, and reveals himself as the villain.
Similarly for Superman 4, I'd have had the two Superman clones (there was a doofed up clone in a deleted series of scenes) be Bizarro and Ultraman, with Bizarro being innocent and Ultra being tyrannical, and have the whole thing focussed on Supes trying to decide how much influence he truly wanted to have on mankind.
