The gang over at First Thoughts gives us a list of the top twenty (presumably American) animated television series. The ban against animated series based on characters from other media strikes me as arbitrary and inconsistently applied besides (Wikipedia says the Smurfs were adapted from a Belgian comic strip.)
Justice League/Justice League Unlimited belongs in the top five. That show's adaption of (and major improvement on) Alan Moore's "For The Man Who Has Everything" is a 22 minute masterpiece about responsibility, the lure of fantasy, and how lived experience can shape and (in a heartbreaking little moment) stunt the ability to imagine (never mind live) an ordinary life.
Yeah, I know I'm taking it too seriously.
The Real Ghostbusters also belongs somewhere on the list.