Well if you are going to steal the plot from virtually every Sci-fi film or story you can think of, you may as well do it big time, and do it so well people will forget you did and just enjoy your unoriginal work of art.
Hah, you don't take an already crappy film and then steal the idea like some did with a film like 'Cyborg', it just breeds a bunch of films ripping-off an already bad film.
Avatar is a type of "Frankenstein's monster' , it is not it's fault it was made, none of it's parts belong to it, but it works when you put it together, 'it's alive', and stronger than all the single entities whose parts it has taken and though it will be attacked and criticised, it will eventually be loved by many. Though I also did a bit of a critical review of Avatar elsewhere, Avatar does what it was intended to do, make lots of money and entertains a new generation of fans who more than likely have never heard of the 1957 novella by Poul Anderson entitled "Call Me Joe".