There's nothing ground-breaking about the story. You've seen it before: Cynical, opportunistic protagonist tries to infiltrate aboriginal people then goes native, finds his destiny and has to betray the evil leaders who sent him in. Not a bad tale, though occasionally heavy-handed in its pro-environment, anti-greed themes.
STORY VS. STORYTELLING But the way the story is told, oh my. The visual effects, fully CGI characters and settings will change the way movies are made henceforth. I'm not usually one who lets "this film blows up good" effects cloud my judgment about the need for a good story at the heart of a movie. The story just barely meets that standard, but the storytelling exceeds it. This is no Transformers 2, which was an explosive but ultimately soulless spectacle.
Avatar's computer-generated characters played by Zoë Saldana (Star Trek) and Sam Worthington (Terminator: Salvation) are utterly believable.
Sam Worthington and Zoe Saldana are the heart of the movie, and they acquit themselves well, even as the stunning visuals threaten to overwhelm every other character, played by a talented though underused cast (including the wonderful Sigourney Weaver); there's just so many of them that it's hard for any (perennial faves Giovanni Ribisi and CCH Pounder, for example) to really stand out.
The villain, Colonel Miles Quaritch, is a pretty standard cardboard cutout; I would've enjoyed an opponent with more style. I suspect Cameron would claim the film's antagonist is really greed and opportunism. Yadda, yadda. Abstract concepts don't substitute for a real character.
The world of Pandora is under attack by greedy humans. Yes, those are floating mountains.
Avatar is one of those grand epics that will initially be judged by its hype rather than its merits. The romance between Worthington and Saldana's characters, combined with the guy's search for himself is probably how Cameron attempts to make Avatar more than a popcorn-crunching epic — indeed, those were the same themes in Cameron's huge box office success, Titanic, but this film's visual effects are what people will be talking about.
The cynics will point to the predictable plot line and Avatar's resulting disappointment thanks to the over-hype in advance of the film's release but, like Titanic, we'll still be debating the success of this film a decade from now when the visual effects will be considered outdated. That's probably a good thing.