Lex Luthor is a super villian in the same sense that Batman can be a super hero. He has nothing more than his intellect with which to try and defeat a god, and that makes him immediately more interesting than anyone else in Supermans rogues gallery (and pretty much every villian fans claim to want to see in future movies with the exception of Brainiac, who I'd put up there with Luthor depending on which version you're talking about). In fact, I liked that he didn't "fight" anyone in the movie. Showing Superman as being someone who doesn't typically have to fight to stop crime and solve problems makes sense for the character.

It was an excellent movie, and a great way to follow up the original movies.

PS: The first one to suggest Doomsday as a good villian for a sequel I will personally slap over the head with a rolled up newspaper.