I kept flashing back to that ill-fated Final Fantasy movie from a decade ago, thinking that Avatar was the film they wanted to make all this time. You've got all the classic Final Fantasy elements there: a tree of life, evil military corporation, powerful woman in tune with the Earth, plucky friends, symbolic tools, etc.
As for the political allegory with the humans' incursion into Pandora, I suspect that it's deeper than many people give it credit for. Sure, at first it seems to be commentary on, say, Iraq, but the more I think about it, it's less about imperialism and more anti-Blackwater. After all, for the humans' faults in the film, some human skills were important enough to help the heroes move along, as well as help out in the final battle.
But that's just me.
I, personally, don't see how the movie's plot could be a commentarty on Iraq. Sure, we've invaded Iraq -anecdotaly- to aquire a resource -oil- but I doubt anyone would look at the Iraq people we were fighting over there as peace-loving, connected-to-the-Earth innocent victims of imperialism.
It's way more obviously a "message" on Native Americans, as the alien tribes were more resembled to Native Americans in culture, belief (connection to nature), dress and actions (thanking a killed creature for giving up its life.)
Overall, I don't really think the movie was supposed to be a "message" about anything. Any reasonable, caring, modern-day person would say that the militristic humans in this movie couldn't be more in the wrong so it seems pointless to make a movie centered around the premise we're supposed to change our minds about something through "learning" about the alien tribes. That's what a message movie should do, change your mind about the subject matter or at least consider the otherside.
Seems to me that the movie wasn't supposed to be a "message" so much as it was just supposed to be an interesting, gripping, story that made us care about the characters and more so the movie was more about the SFX ejaculate.
It's a shame that Cameron poured so much attention, work, and sweat into the SFX but the story got almost no attention at all. In a way it's simillar to the poblem Lucas had with the prequels, so much poured into the FX and spectacle and almost none poured into the story.
Now, where Cameron beats Lucas is that at the very least the characters here are far more interesting, engaging, and easier to connect with than the characters in the prequels and where the prequels were more about showing off effects (Hey! We need to have a CG space-race here! Because it'll look cool!) or coreographed fights, this movie at least made the FX serve the plot a bit more. The sequences came more naturally and the fight scenes and battle scenes were very well laid out and the final battle between our hero and our villian was less ballet and more brtual.
The story in this movie is "good" if pedestrian and has been told before but Cameron tells it fairly well, it's just nothing special. If the guy had spent another year or so developing the story after he devloped the FX he'd really have something here. As it is, the movie is a visual masterpiece with good action sequences but without a good story there's little reason to revisit it.