*throws up*
Don't forget THE POOP THAT TOOK A PEE, narrated by Morgan Freeman.
"Why are we here?" Douglas cried, as poop came out of his wiener in a long, thin strip.
(Best literary novel ever quasi-made)
In seriousness, um...what was the question?
Right, the villains. It depends on the story. Sometimes the villains are sort of throwaway nothings, just something for the MC to strive against, so...they're there, as a plot device, which is fine, but not brilliant. You could replace Voldemort with an evil big red dog who wants to eat everyone, basically. (I mean, I'm exaggerating a bit, but you get my point.) Harry Potter could go toe to toe with a different villain or evil force--he just needs an evil force.
Cartman is the most brilliant f****** villain I've ever come across. Ever. In any medium. He's not replaceable; South Park would not be what it is without him; he's not just an evil force (though that is certainly part of it). If Harry Potter went up against some wizard version of Eric Cartman, it would have been an entirely different storyline...
A much more twisted storyline...
As to which is "greater", I'm gonna say...it sort of depends on what you set out to write. And how you write it.
In other words, I'm a dumbcrap and I dunno.