Ren & Stimpy and South Park probably come out on top, Aeon Flux is up there, older things like Duckman and the Tick trail behind those a little, and I do enjoy Futurama and the Simpsons.
Out of the more 'kiddy' stuff the animated Batman is excellent, Star Wars : Clone Wars was very good, I was impressed by the Chronicles of Riddick OVA thing, Samurai Jack is good and Animaniacs had its moments.
Clone High was good too.
There are bound to be a lot more.