Afraid the last "great" Russian film I saw was "Oblomov"
Unfinished piece for player piano (by the same director) is much, much better.
The greatest ever Russian movie, however, is Andrei Rubleev, a three hour plotless, black and white, fictionalized biography of a 15th century icon painter (almost nothing is known of his life)
It's really one of the crowning achievements of movie art and it's impossible to recommend it too highly (it works better in a theater than in a living room). The early violent sequences are harrowing, but the final sequence about a young bell-maker dealing with the unexpected death of his father is incredibly moving.