Pocohontos? Hardly - Poco went back to the UK with John and died soon after. Not a happy ending, really. And it's not quite Dances With Wolves either, though there are some good comparisons. I actually thought Weaver was just reprising her role a bit from Gorillas in the Mist.
Lucas was a huge copy-cater. Look at any Kirosawa film - R2 and 3PO were inspired by The Hidden Fortress and were supposed to be the only two characters to be in all (planned) nine films. It's very much the Seven Samurai, and he borrowed from many archetypes. The Death Star trench borrowed heavily from The Damnbusters right down to some dialog.
Sometimes it's not the originality of the story, it's how it's told. Everyone knew the story of Titanic too but it was a great movie. I mean, there are only so many "stories" after all.
The best description I've heard was "it's the old cowboys and Indians story from the past, but this time the Indians win".
Then again, we have no idea what happens afterwards. Perhaps they all die of a human cold.