If you want to talk about films that elevate genre filmmaking to new creative plateaus, I would talk about stuff like The Searchers, 2001, Once Upon a Time in the West, Night of the Living Dead, Blade Runner, etc. I don't think anyone has made that claim about Avatar unless they're talking about its ability to completely transport the viewer to a new world, in which case it does break new ground and then some.
I don't take issue with the plot being predictable because that isn't the point. The plot was pretty much given away in the trailers. A movie like this isn't about keeping you guessing, it's about taking you on the journey. And regardless of whether or not you knew what the major plot points would be, I'm pretty certain you didn't know how those plot points would be implemented, which is an area where Avatar really shines.
As for your issue with the exposition, I'll just say that I disagree entirely. I thought the first half of the film was absolutely brilliant. Why did you feel it was clumsy? Some of the dialogue was clumsy, but the pacing and buildup was fantastic in my opinion. You see Jake go from being a cripple in a wheelchair to walking and running, and from there to flying. You go from these narrow, confined spaces into a huge, open world over the course of that first half. You take part in his joy and exhilaration. That was the point of the movie, not to keep you guessing about what plot twist would come next.
Also, linking to that Willco post doesn't do much for your argument because 1) It's a Willco post, and 2) he cherrypicked reviews to make his case. You could just as easily find plenty of reviews that state that the story is well-told.
I have quite a bit to say about the "It's manipulative" part of your post, but I'll have to save that for later.
Edit: Ichirou, your reading comprehension skills are about as bad as I've seen on this forum, and you use almost as many fallacies as Willco.