Avatar was hardly original as it comes to the root story. I rather think of it as The Last Samurai by way of Ferngully, The Last Rainforest with Jake Sully's character being a commingling of Captain Nathan Algren and Zak Young, respectively.
The telling of this story, however, is quite another matter, particularly in 3-D. The rendering of the Na'vi was completely credible, nevermind all the creatures which inhabit their realm. It was the film in motion which really sank the hook insofar as pulling me into the story of Avatar. While the film indulged in very few if any 3-D "cheap shots," the addition of that third dimension had the effect of more fully involving the view in the action on the screen. The flight and battle sequences were especially effective in conveying a more detailed sense of perspective and distance.
When movement was excessively fast, there was a tendency for the overall 3-D image not to cohere fully, and I wasn't particularly surprised by this, as I've seen my share of 3-D movies which "sort of" worked. These incidents were not frequent and it may be that my eyes were adapting better to the experience as the movie progressed. The fact is, Avatar is, far and away, The ... Best ... Three ... D ... Movie ... EVER ... MADE.
I agree that the story is pretty unoriginal. I see it as the story of Pocahontas wrapped in a Ferngully mask. Even though the story is unoriginal, the storytelling is amazing. I've seen the movie three times now and I still feel like I could cry every time in the final battle scene. The experience gets you that involved the story.
I liked it so much, I had to see it twice. I liked the fact that it wasnt in a galaxy far away... somewhere. It was based on actual geography. Alpha-Centauri solar system. I wish they explained how they actually traveled to the moon Pandora from Earth in only five years (a feat seemingly impossible) with no wormhole required. They didnt need actual science but some kind of explanation to excite the imagination would be nice. Pandora, as seen by humans a terrible and harsh planet with one reason to be there. Money. It takes you through a journey through the eyes of a man becoming pandoran and seeing the beauty (instead of a horrible place) in all the nature the moon has to offer. It has you rooting for the alien in this one and seeing the human as the bad guy intruder. A different take on a story if you ask me.