So I just became one of the last SF fans in America to see James Cameron's Avatar.
Against my will, I love it. I think it is the sheer beauty of it. The story is common and predictable. The characters are fine but nothing noteworthy. The dialog is better than Star Wars, for what that's worth. Nothing happens in the plot except to set up for the climax (that is, if you meet an animal, or if one is even mentioned, it'll be in the climax, and whatever was said about it when you first met it will be the critical feature). And the world-creation is simply sloppy.
It's this last that boggles my brain the most, because in some ways it is the world that is so attractive. But time and again, I was jarred out of the story by biologically implausible features. I'm not talking about the planetary neural network, that's plausible. I'm talking about contradictions in evolutionary biology. The Na'avi don't appear to come from the same evolutionary tree as the rest of Pandoran life. They have a completely different respiratory system. They have a redesigned skeleton, with four limbs instead of six. They have one "bonding antenna" instead of two. They are the only life form on Pandora with hair.
Of course, James Cameron has never been terribly good at science fiction. In Alien the larva dissolves a vacuum suit with acid, without, somehow, venting the suit. Terminator resolves the time-travel paradox with the destiny solution, and then Terminator 2 invalidates the temporal laws that made the original work, by using parallel futures. (Which is to say, in T1, the efforts of the people of the future to change the future are the events that create the future. If you try to kill your grandmother, she survives, and meets your grandfather at the hospital). In T2, one can do something so that the future event that allowed you to be there never occurs. You can kill your own grandmother.))
Okay, these are geek issues. But there are a lot of geeks in the world. And it only takes a little thought to avoid these events that interrupt his story. I'll admit that the time travel paradox was a systemic problem that could not be resolved in the story he wanted to tell. He would have had to tell a completely different T2 to fix the problem, and I'll grant him some slack in not wanting to do that. A little. But in Avatar the problems are easily fixed without any plot impact. He could have left out the 3/4 second focus on the breathing holes of the animals, or tucked subtle breathing hole on the Na'avi (say, under the armpit). He could have had a mix of limb count among the creatures. The Na'avi could have had two braids instead of one. Simple, easy solutions. Most would add to the world. But he just didn't bother.
He made the Na'avi SO different than Pandoran fauna that I wondered a couple times during the movie if, in fact, they were a transplant from some other world. I mean, Cameron left so many clues that they didn't belong... but it turned out that their belonging was the essential theme of the story. Gee, James, that didn't work the way you wanted it to, did it?