Will we ever make it to 250?
War and Peace should be on the list -- it's a phenomenal epic that's been praised here frequently.
We've already had it on other lists, but I suggest adding Mother Dao the Turtlelike. It's one of the best examples of unearthing and arranging silent footage to create something fresh and vital. I just wish there was a better restoration of it.
I think there should be something from the Sensory Ethnographic Lab. Leviathan is the easy choice but I'm not 100% sure it's the best choice. While I have seen some of their other projects, I can't say that anything beats it.
I also suggest including Werner Schroeter in some way. I'm just a casual film watcher so I haven't done an exhaustive study of his filmography, but I was amazed by The Rose King. If it wasn't so homosexual it would be one of my personal favorites. The film is hard to put into words. It plays out like a mood piece with lush visuals that's heavily dependent on the editing.