It annoys me when people say that Superman doesn't have great villains.. What?! It seems to me he has a very healthy rogues gallery that can challenge him in different and interesting ways.

Now, I'm not an expert since I don't read all the comics, but I've seen enough Superman from all media to realize he has good enemies with interesting backgrounds and stories.

The ones that come to mind are:

Lex Luthor
Bizarro
Parasite
Cyborg Superman
Brainiac
Mr Mxy
Darkseid
Metallo
General Zod
Mongul
Doomsday
Lobo
Toyman