Let me start this thing out proper; "Avatar" is a movie you should see. If at all possible, you should see it in a theater equipped with the newfangled Digital 3-D and some laughably complex sound system. A great deal of love was invested in the production of this film, and it does deserve your $13 (or whatever) and 165 minutes. You will experience, for nearly three hours, visual feasts the likes of which you simply have not ever seen.
However, it is not a particularly good movie, and if you will permit me a moment I will explain why.
The inspirational speeches are neither inspirational nor, according to my lofty standards, speeches. I often found myself wondering why, with all the money they spent on absolutely everything else, they couldn't have hired whomever wrote Bush's second State of the Union to contribute some better lines.
The story is a decently-constructed one-sided criticism of corporatism and warfare. But every character we meet is disappointingly one-dimensional. Hey. See what I did there?
Despite being set in the distant future most of the people appear to be English-speaking Americans. I'm pretty sure this only bothers me because of how much I miss Firefly.
The Na'vi, transparent metaphors for Native Americans (or Iraqi citizens), exist in some kind of impossible Utpoia, embodied in the line spoken by the corporate executive; "We have nothing they need." This seems to be an argument against all technological progress, which is a strange message to come from a man who invented 30 different technologies just to tell a story.
I could go on, but everything else is really just nitpicky examples of what I've already pointed out. Some points in the film are forehead-smackingly stupid, which can really suck you out of the experience.
An ironic twist: Sigourney Weaver, who played Lt. Ripley in James Cameron's "Aliens," makes an urgent plea for compassion toward a violent alien race in "Avatar." Everyone remembers her line from "Aliens," right?
"Take off and nuke the entire site from orbit. It's the only way to be sure."
Ultimately, none of this stuff matters. "Avatar" is a force of nature and you would be doing yourself a favor if you went and saw it. Just don't expect to feel like you did after watching "Braveheart" for the first time.