The uncanny valley is the revulsion caused by robots and computer generated images that try to mimic human faces. It was coined in the 1970’s by Masahiro Mori (link) and is the reason why watching Polar Express makes me jump up and down like a rabid chimpanzee. CGI movies that maintain their cartoony-ness avoid this problem.
So it was with a bit of suspicion that I went to see Avatar, expecting to jump up and down like a rabid chimp as soon as those blue goat people got on screen. I was wrong. James Cameron understood this implicitly and created an image capture system that follows actors facial movements and maps it directly to the blue Navi’s. The actors are really acting and the computer generated animatronics are imbued with emotion that greatly exceeds that of the actual human actors.
Avatar is great in the way that Titanic was great. The main character in Titanic was the ship, and in Avatar, it’s the escape from uncanny valley. The script is a Disney princess movie on steroids, but the real reason you should see Avatar is this entirely new way of experiencing the world.
I have to add, I have always felt virtual reality won’t work until all five senses are involved and Cameron seems to understand it as well -to access the avatars, the characters lay down in an MRI machine -it is through electromagnetic manipulation of nerves that true telepresence will be achieved.