It's not an anime, plain and simple. I hear this discussion a lot, but let's look at the word "anime". In Japan, it simply means animation, but it's used over here to specifically refer to Japanese animation. The word is Japanese in origin, not Latin like most of the English language. As such, the word itself already excludes Avatar: The Last Airbender.

To me it's very cut and dry, I don't believe anime is a style, but based on origin. It's much like how Korean title their form of "manga" as "manhwa". If you say I'm reading a manhwa, people will understand you're reading a Korean comic.

I think the line blurred for many people due to the fact that anime is such a fandom aimed at the younger generation who think they can turn words into slang (as in sick can mean bad or good). I don't believe anime can be defined just as a style, and thus anything ever in that style is anime. If this was the case it would be hard to understand what was and what wasn't since anime styles change, and people are influenced throughout the world from their favorite cartoons. It's like turning the word anime into meaning cartoons in general.

I feel like if Avatar is accepted as an anime, then you might as well accept Johnny Bravo (USA), My Gym Partner Is A Money, Drama Island (Canadian), etc. We have a word for those things though already, it's called cartoons.

These are just my beliefs though.

______________________