Dances With Wolves (1990).
I've been slow in continuing this top 10 list, but to recap: #10, Field of Dreams; #9, Night of the Living Dead; and also-rans which did not quite make the cut: #11, Butch Cassidy & The Sundance Kid; #12, Godfather Part II; #13, Rocky (part I); #14, The Sting; and #15, The Outlaw Josey Wales.
But back to Dances With Wolves: In addition to the wonderfully magnetic cast, orchestral soundtrack (which is God-awesome), scenery, and cinematography -- to me, the most significant and overarching (and yet simple) message of this film was as follows: Don't buy too much into the stereotypes of groups of people whom society says are "different" from you because they come from a different culture and way of thinking, and don't embrace the too-often resulting viewpoint that you should be fearful, hateful and warwongering towards "different" people. Instead, before you do too much of anything, go try to get to know and talk to those people. You just might find that the stereotype bares no resemblance whatsoever to the truth.