Because they comes from a country with a vastly different religious, cultural, and historical background, Japanese cartoons naturally have a distinct style to them.
Avatar seems to have done a phenomenal job replicating that style.
So well, in fact, that if you didn't know it was made in America, you might have mistaken it for an actual Japanese cartoon.
So I guess the answer depenRAB not on what you think of Avatar, but rather on what you consider anime to be.
If anime is merely a cartoon from Japan, then Avatar isn't anime.
If anime is a genre of cartoon with a distinct style that originated in Japan, then it could be.
Personally, since I don't have a degree in film, literature, or animation, I can't say one way or the other... nor do I personally care, really.
Anime is a distinct style... anime can only come from Japan.
It's like arguing over how to pronounce "tomato."
The only thing I can say is that Avatar is a great show.