To me this is a no-brainer. American cartoons are definitely superior. ha ha
I think American cartoons are much more diverse, Anime seems all alike and rather angsty. They also seem to be drawn alike as opposed to the many different styles of American cartoons. You had the realism of a Johnny Quest and the caricatures like the Flintstones. People didn't even scratch the surface of American cartoons, besides classics like Johnny Quest, the Flintstones, the Jetsons what about Quick Draw McGraw, Yogi the Bear, Huckleberry Hound, top Cat, Tom and Jerry and modern classics like Dexter's Lab... and that is just Hanna Barbera.
Warner Brothers gave us Daffy Duck, Porky Pig, Bugs, Tweety & Sylvester, Pepe Le Pew, Speedy Gonzalez and every one knows those were not just for kids, the undertones kept adults smiling too. Modern WB gave us Pinky & the Brain and the Animaniacs.
Jay Ward was brilliant with Crusader Rabbit and his follow on, Rocky & Bullwinkle and Friends. Every body gets that R&B, Dudley Do-right, Mr. Peabody's Improbable History, Fractured Fairy Tales & Aesop's Tales were geared towards adults and kids laughed because they were silly.
And that is with out even mentioning the Walt Disney Studios and all they did and continue to do with cartoons as an art form.
Even Disney Channel has entertaining cartoons like Phineas & Ferb, American Dragon and Kim Possible.
Others have mentioned the modern creations of South Park, the Simpsons, Family Guy and King of the Hill.
What would the holidays be without A Charlie Brown Christmas and the Grinch?
Did I also mention the incarnations of Superman, Batman, Fantastic Four, Green Hornet, etc. that have appeared over the years?
So yeah, I'll take American cartoons.