Avatar is a movie that brings a components of every reason we go to the movies: Action/Adventure, Love/Romance, Story, you name it. It's an understatement to say that the CGI, Imagery and Sensory Overload is what drives this movie. But I think that was Cameron's point wasn't it?
The Story itself is a little bit Dances with Wolves meets Inconvenient Truth meets Transformers.
But it's HOW the story is told that changes the game. The colors, shapes, movement everything creates a visual and audible ballett that "washes over you" (especially when seen in 3D).
By the time the film ends, you will wish you were on Pandora and could be an Avatar!