Lord of the Rings: Return of the King
Rather pre-emptive, I know, but anyone who's read the book should be able to talk about this.
The Battle of Pelennor Fields is said to be the greatest undertaking in movie battle history. The trilogy is hailed as the greatest fantasy movie ever. The characters are enticing, the symbolism profound, the story heart-wrenching, and this is, without a doubt, a movie that will stand the test of time. In 60 years, people will still be talking about this movie, not just because of the special effects, but because it speaks to your heart, it tells you, no matter how impossible it may seem, there is ALWAYS hope.
Note: I purposely kept this post vague, but anyone who has not read the book, and wants to be pleasantly surprised when they see the movie, don't read future posts, b/c there WILL be spoilers.