Tokyo Story
In Tokyo Story (1953) an elderly couple leave their quiet home town to visit their children (and grandchildren) in the big city of Tokyo. Upon their arrival they find that they are almost a nuisance as their children have little time to spend with them. Instead, it is the widow of their dead son (slain in WWII) who shows them the most affection.
The film is directed by one of the Japan's greatest directors, Yasujiro Ozu. Tokyo Story is often cited as being his masterpiece.
I must point out that the film moves at a very deliberate and unhurried pace. It is by no means boring, but this is not the kind of movie to see when you're not in the mood.
Special mention must be made of the film's look. Ozu apparently prefers to work with a static camera, a technique which I generally find boring. His style is the exception, however. The camera may be static, but the shot composition is interesting and the camera has the habit on lingering on certain details (all of which are filmed from a low angle).
I cannot verify whether this is Ozu's masterpiece (it's the first Ozu film I've seen). However, I can see why someone would call this a masterpiece not only of Japanese cinema, but of world cinema.