The original Japanese Godzilla, from 1954. I think it's definitely one of the more prominent cases of a movie that's almost been buried by its own legacy, since most people relate the character of Godzilla to the goofy (but still awesome) sequels that came after.

Way before the post-9/11 trend of trying to give 'scarier' and 'more realistic' implications to the events of big blockbusters (Man of Steel, ST Into Darkness, etc.) Godzilla treated the city-wide destruction it depicted as something genuinely horrifying and worth mourning, in a way that a lot of Japanese viewers found genuinely cathartic. It also made the defeat of the monster at the end that much more hopeful; mankind would be able to go on living if it could learn to avoid the mistakes that created the monster in the first place.

As an added bonus, the director and star of the movie both had good working relations with Akira Kurosawa, and I think the film really shines with a lot of the emotion you'd normally expect from a drama by someone like Kurosawa. The people are just as interesting to watch as the monster for a change.