Avatar is perhaps one of nick's best shows. It was a show which can be liked by pretty much anyone. However, unlike most of nick's other show, avatar has actually ended. Most nick's show never end(i.e. fairly odd parents, drake and josh, etc.).
Avatar actually had a long-going story which was beautifully conducted.
But here is the problem as i see it: its too good.
Nick is a channel designed for kids, but this show is designed for everyone. It doesn't follow nick's normal standard/style of shows. It is simply not designed for nick.
I personally would like to see this show go on for ONE more season(any more and it would lose its awsomeness). Then, it could build side stories(adventures of airbenders?, past avatar shows, etc.).