OMG!
Read this:
http://www.cinemablend.com/new/The-Avatar-Trailer-Sucks-But-Don-t-Give-Up-Hope-14448.html
This is just a fucking trailer, you'll be able to judge once you HAVE SEEN the 15 minutes, you have to see the scenes and not just shots of 4, 5 seconds. This is exactly what is said in this link:
"I get that they're trying to follow up on the promises that Avatar looks like nothing ever has, and would rather show off as many flashy scenes as possible rather than ease you into this world. But the Quicktime format is so limiting, especially for a 3D movie, that the impact of all the CGI wizardry is muted anyway. Already people are complaining that Sam Worthington's Avatar doesn't look realistic, that the blue skin looks fake, because they haven't had enough time to see it move like a human, hear it talk, or see it respond to its world. Having seen it in Hall H, I promise it works. It just needs time to settle in, and just by showing one complete scene at Comic Con, they sold the effect entirely. Cutting together all the random scenes in the trailer just makes you more disoriented."
Watch it in HD, pause on shots like when Jake stands up and sees his feet moving, when he says "it's great", or even on Neytiri, it really is realistic, watch for all the subtle things.
And you all say that it doesn't look realistic because of the colours, very colourful, if it was darker, it would look more realistic (but it already looks realistic)