I gave this 4 stars based solely on the amazing imagery experienced while watching this movie. I've never seen anything like it. It actually made me dizzy at times!
Why not 5 stars? The story is certainly one we've seen before (See Dances With Wolves, Pocahontas etc). It was also a bit long. 3 hours in a movie theater definitely cramps your legs.
All and all, this is one movie that you really have to see before it leaves the theaters.