Some notable omissions, just off the top of my head (and I concede that the English-language bias is still too strong):
-Man With a Movie Camera: Dziga Vertov
-Nanook of the North: Robert Flaherty (for the historical significance alone)
-Hearts of Darkness: George Hickenlooper
-7-Up: Michael Apted
-Hearts and Minds: Peter Davis
-Olympia and Triumph of the Will: Leni Riefenstahl (I'd choose the former)
-The Sorrow and the Pity: Marcel Ophuls
-The War Game: Peter Watkins (though I understand why some would contest this)
-When We Were Kings: Leon Gast
-Primary: Robert Drew
The 10 I would lose to make room for these:
Gimme Shelter, Grey Gardens (One Maysles is enough, and Salesman is it), Fog of War (one Morris is enough), F911, Bowling for Columbine (seriously, is there anything about Moore, his concerns or his style that you can't understand from Roger and Me?), Super Size Me (probably the least deserving film on the list), Woodstock (too many music docs already, and this loses to Don't Look Back), Spellbound, Inconvenient Truth, and Capturing the Friedmans (all three too recent).