Let me start by saying I believe Superman has the most underrated rogues in all of comics. Lex Luthor, Darkseid, General Zod, Brainiac, Parasite, Metallo, Toyman, Doomsday, Mongul, Silver Banshee, Bizarro, Livewire, Mr. Mxyzptlk, etc. I think they’re great. And the Phantom Zone is the absolute coolest prison for villains out there.
To me, the problem is that Lex Luthor is so iconic he gets all of the focus from new writers. They do the same thing with Dr. Doom and the Fantastic Four. Everyone gets so excited at the prospect of writing him that the other villains get over looked. It’s the same with Luthor. I love him as a villain; he’s very complex and interesting. No one really takes the time to flesh out and expand the stories of his other villains. Everyone can point to a great Luthor story, but if you’re trying to find one about Parasite or Livewire you’re going to struggle.