Just a rehash of the Abyss

Don't forget the "mother" aspect. Mother the ship's computer in Alien, Sarah the brave mum in Terminator, Ripley the brave surrogate mum to Newt in Aliens, Grace being considered "Mother" to the Na'vi in Avatar.

In the Abyss, there is almost no interaction with the aliens at all. We don't even know they're aliens until the very end. And there wasn't an environmental statement in Abyss, either, but an anti-war statement. The only points of similarity are pretty universal for a great percentage of all fiction. The similarities are pretty few and far between.

Avatar is, however, a rehash of Dances With Wolves, the plot being near-identical.

A soldier in an army which is fighting against the natives is integrated into a native tribe. Gradually, he sees the error of his ways and adopts their culture, eventually fighting against the army he once served. At first he is clumsy and awkward, but eventually he becomes better at being a native than the natives themselves. He falls in love with a native woman (actually a white woman in Dances With Wolves, but she was fully integrated in the tribe), and a native man is jealous of this foreigner's rapid rise in station - and he is also a rival for the woman's affections. In the end, he comes to respect the foreign protagonist.