I wouldn't say I have a "favorite" cartoon, but I started watching Futurama again on Netflix and have to say, it's pretty much just as funny as I remember it. The great thing about this show is the absolutely horrible notion of moral clairty.
With the two main characters, Fry and Bender, there really is no knowing how deep the debauchery will go in each episode, and I am always pleasantly surprised when they decide, "You know what? There is no moral to this story, lets just let them all get away with eating an entire alien race."
It's definitely a fresh change from the normal, and actually does a good job poking fun with constant pop-culture references and over the top, poorly done, voice acting.
What is your favorite cartoon? Do you even watch them? Personally I love Netflix, I don't even pay for cable anymore…