This is a strange one to grade. You see, the first 2 hours of this movie are among the best I've ever seen. The cinematography is astonishing: each frame is a work of art, and each scene has its own distinct look and feel. This owes a lot to the absolutely staggering live-action sets and set pieces; this simply wouldn't have been anywhere near as good with CG. The acting is top-class, each character feeling completely real - something essential to the movie's goal of truly showing what war is like. And by god, does it reach that goal: no other movie has as effectively communicated the emotions, the despair and the moral conflicts as this one. It avoids the clichés and replaces them with genuine grit.
But. The last 30 minutes are a strange thing. While the cinematography remains overwhelmingly gorgeous and the acting loses none of its authenticity, the tone and story of the film seem to go out the window. We are presented with a discomforting, ambiguous, anticlimactic sequence that goes against all the wonderful build-up of the last 2 hours.
I certainly get what Coppola was trying to achieve: without spoiling it, this sequence was attempting to play with the audience's emotions in such as way as to make them feel the conclusion rather than to actually have one. The entire point of the movie is that whatever happened in the first 2 hours would only lead to the circumstances of the last 30 minutes. But to me, that simply wasn't enough. I was getting gradually more excited at seeing what this mythical Col. Kurtz was going to be like, what motivated him... and the movie certainly implied that the answer would be massive! But no, instead we have an artsy confusing mess of an ending that airily attempts to deal with Marlon Brando's obesity, and only halfheartedly comes up with a few meandering sentences to explain what the whole journey had been for. It's disappointing.
That being said, the movie's strengths are still colossal enough to overshadow this glaring flaw. Perhaps I simply didn't get it, as others clearly loved the ending very much. To me, while it is a sad waste of potential, it isn't enough to cancel out the fact that this is probably the best war movie I've ever seen.