Originally Posted by Lead Cenobite
You can get plenty of story out of a single villain, and even I'll admit the movies haven't made the best use of him. There's Superman, but Lex is somewhat marred by the comedic sidekicks, he's only a supporting villain in II, he's a bit closer to the comics version in IV but that's wasted on a bad movie, and his plan in Returns is just ridiculous.
If the villain is someone like Bizarro, Metallo, or Parasite, you can easily work him in as the one pulling the strings, or even the one who created them.
The thing with Lex Luthor is he is the name of Superman's enemy, but what he is beyond that has changed a huge amount over time. STM, L&C and STAS have very different Lex's. True, he is more similar in L&C and STAS, but still quite different. In STAS he is an arms dealer, who clear operates near the edge of the law. In L&c he is a businessman and philanthropist, most of whose official actions seem above board, except maybe his fast-tracking nuclear power plants, but he secretly recruits gangsters to drive down the price of land he wants and lots of other illegal actions.