As firehawk said, it's not the unoriginality of the story trope - it's which story trope has been chosen. At least for me, that's what stuck out. That and the awkwardness of setting a story in the future which seems to require humans having forgotten a huge chunk of their own history.
Oh come
on! Our history is much more recent, and we still keep making the same mistakes over and over. And what bothers you is that a couple of hundred years in the future people don't remember history better than we do?
Even today, when America is fighting a war that involves occupation - it's not the same thing as what happened during the Age of Colonization. Avatar's trailer seems to show a military-industrial complex overtly seeking to move a group of "primitive savages" off a piece of land so that they can take the resources of that land. Making it so overt seems very 19th century. Interestingly, when Cameron discusses the historical precendents for his tale in the linked interview, he primarily uses examples from the 16th, 17th, and 19th centuries, though he does briefly mention oil. Versions of colonialism still occur, sure - just not this version where everything's so out in the open. So a choice has been made to make the villains extremely Mwahahaha villains - because we all know that it's evil to just walk in and steal some other culture's shit so you can sell it for profit. As I said in my original post - that feels ham-fisted to me.
This original version is a Discredited Trope, but in modern-day fiction — particularly in Hollywood movies — Mighty Whitey pops up, not as the product of a white supremacist viewpoint, but the result of creative types trying to appeal to as broad a cross-section of society as possible in order to get their cash back. And since the majority of major Hollywood stars are white Americans (despite the fact that only a small minority of their audiences are Americans at all, let alone white Americans), it's almost inevitable that the all-singing, all-dancing hero is also going to be registering low on the melanin count.
And
that's the part that is uncomfortably unoriginal. Does that make sense? It's not the
unoriginal that's feeling wrong, it's the
uncomfortable.
So let me get this straight... You are upset that Cameron cast a human actor for when he should have cast a real alien to play an alien? Or that this 'trope' is only acceptable if played by a non-white actor?

Seriously... you are reaching.
I'm not reaching. I simply stated my opinion of how the trailer struck me, and various folks have been arguing with me about it. Unfortuntely, you and others keep arguing against something I didn't say. The point has to do with
this specific trope - and yes, this specific trope has to do with how mainstream American fiction deals with whiteness and exoticizing the "Other". Traditionally that means non-whites, here, as often in SF, the "Other" is presented as aliens. But it's still the same trope, and it's still a white guy's story of entering a native culture, and even a completely alien environment, and then mastering it the point that he leads the natives in battle, which does still have overtones of the innate superiority of the white guy, especially since this is one in a long series of this kind of story.
Add in the description of the Navi by the bad guy as "primitive savages" (who we as the audience can tell are really Noble Savages living in Peaceful Ecological Beautitude with their Perfect Unspoiled Environment) and you're then trying to have your cake and eat it too. You're pulling out a Politically Correct Mighty Whitey.
Firehawk's idea of using a non-white actor would at least avoid some of that.
I've got no argument with anyone who doesn't care about these issues. I'm sure this movie will be imminently enjoyable as a rip-roaring adventure tale. I'm just talking about what I personally noticed.
We can quote TV/movie "tropes" until the sun goes dark, but it doesn't matter much. Sure, Avatar may use a distinctive 'trope', but it is hardly a common one, or one of the most common ones. Just look at all the romantic comedies, cop dramas, sitcoms, and mysteries where 'tropes' are repeated more often that one cares to count. (The complaints about 'tropes' in this thread is also turning into a 'trope' of this forum)
Again, it is the execution that matters.
Not when you're using an outdated trope. For the third or fourth time, it's not the fact that the movie is based on
a trope - it's the trope that the movie is based on. And it's the way it appears to be handling that trope - which is not only in an unoriginal way, but with its metaphors being more appropriate to an earlier time. Like I said above, it seems to be making for Eeeevilll Villains, and Mary Sue-ish good guys in the Navi. That's a turn off for me.