Even before the movie was over, I knew the haters were going to sound off about the overrated state of James Cameron’s Avatar, primarily due to the derivative nature of the plot. I thought Oh, so it’s like Dances With Wolves Meets The Matrix. That’s cool. And it is, really.
Update (4/9/2010): Since this is such a popular post, I highly recommend perusing my updated opinion on the nature of this story.
That is the main complaint right out of the gate, though, and even startup buzzkill complaints like what frakking font they used for subtitles can’t escape the comments section mob. They all huddle under the banner of Originality. They decry the sin of spending so much money on a project, and not letting some of it go to a creative story. I’m on the opposite pole. I think Cameron’s shrewdness is stellar, because “creative” can often spell doom to a film as ambitious as this. If I was investing 300 million on a world like Pandora, I would want to tell a story that’s tried and true. Tested and well-received.
Dances With Wolves and The Last Samurai told similar stories, yes. But we eat that shit up, and therefore it’s not lazy of Cameron. It’s a business decision. Anyway, setting that nitpick of story aside, you have a serious success in the presentation of a movie. And, the next big step in visual effects, especially 3-D technology.
I can think of another movie that took one of those big steps, and its story was a blatant rip-off of every myth story imaginable regarding The Hero’s Journey. What was that film called, again? 
The Litter Box 
Just came across this. Perfectly agree with what you said. 3D filming techniques are VERY hard to master. Especially minor and subtle things like the depth of the scene. Too much depth change can make the audience feel sick. The correct implementation of 3D elements can completely immense the audience (burning amber), while excessive use can make the scene look displaced and jagger.
A LOT of 3D techniques were employed but people don’t notice it. The improvements from other movies like The Final Destination and My Bloody Valentine pretty much brought 3D movies from being a gimmick to a worthy story-telling format.
Cameron was wise in using tried-and-tested storyline and casts so he can focus on the 3D side of things.
That is an interesting point about JC’s possible motivation for a “safe” storyline. I remember feeling the same way about ‘The Matrix’ when it came out. I was young and wanted to “show-up” all the people who lost their mind over this film. I would rattle off a list of the stories it seemed to crib (such as the Terminator and Dark City). But in the end, you just have to relax and enjoy the original effects and vision these films bring.