The story in Avatar has been told many times before.
Dance with the Wolves, Pocahontas and even Fern Gully comes to mind. So obviously the plot as many reviews have stated isn't very unique.
The main twist though is the Avatar concept, which led to many tense and immense action scenes.
Perhaps even more alarming is how real the alien race looked and blended with the Sci-Fi sets, props and human actors, let alone the beautiful and immersive scenery.
Definitely one of my new favourite movies of all time, BEST use of 3D by far!