From a Game Artist's standpoint...
Animation wise, American Cartoons generally have more fluid animation since they usually have higher Frames-Per-Second rates.
Art Wise, Japanese Anime is faaaaaaaaaar faaaaarrrrr superior in terms of art...like...its not even a contest.
Story wise...derp. Anime wins here by default, 95% of American toons are episodic with very vague long-term stories. Anime on the other hand is very story driven (setting aside gag series)
Something you have to remember about Japanese Anime, they run 3 dozen new series every 3 months, as opposed to America's 1 or 2 a year. In that regard, the Japanese absolutely trounce the USA.
This entire argument is dependent on the time period of animation we're talking about.
If it's the 80's/90's...America wins HANDS DOWN...not even remotely a competition, Disney was absolutely amazing back then - it doesn't get better than Disney.
If we're talking about 00's/10's... Japan wins hands down.
...uhh...ill just put my favorite quote of all time here.
"Welcome to Pain, the second of three...You have dealt the first...now deal with me!!"
