It's fulfilling to step back at some remove and acknowledge just how extensive a contribution documentary has made to the art of film. It's not a marginal enterprise: documentary has always been critical to the development of cinema aesthetics. Many other titles belong here; the first draft of this list was comfortably twice as long and could easily have hit 250 titles without lowering standards. Enjoy the richness of the list rather than carping over the omissions. Dates and titles are from U.S. release. Notice that the list is almost entirely American, with Joris Ivens and some Frenchmen thrown in. There are also no real ethnographic films. These limitations are mine, not those of the films. As penance, I've deliberately left off any documentaries about the movies.
The work of Eadweard Muybridge (precinema)
The films of the Lumieres (1896-1899) Execution of Czolcosz (1901), Life of an American Fireman (1903), Edwin S. Porter With Captain Scott RN at the South Pole (1912), Herbert George Ponting
Manahatta (1921), Paul Strand
Nanook of the North (1922), Robert Flaherty
Berlin: Symphony of a Great City (1926), Walter Ruttman, Karl Freund
Moana (1926), Robert Flaherty (but not the family "restoration")
Living Russia; or, The Man with a Movie Camera (1929), Dziga Vertov
The Silent Enemy (1930), H.P. Carver
Land Without Bread (1932), Luis Buñuel
Que Viva Mexico! (1937 abridged version/1939), Sergei Eisenstein
Man of Aran (1934), Robert Flaherty
Night Mail (1935), Basil Wright, Harry Watt
Triumph of the Will (1936), Olympia (1937), Leni Riefenstahl
London Can Take It (1940), Luten to Britain (1942), Fires Were Started (1943), A Diary for Timothy (1945), Humphrey Jennings
The Land (1942), Robert Flaherty
Four Men on a Raft (1942/assembled 1993), Orson Welles
The Battk of Russia, Prelude to War, Divide and Conquer, The Nazis Strike (1943), Frank Capra, Anatole Litvak, Anthony Veiller
Memphu Belk (1944), William Wyler
With the Marinu at Tarawa (1944), U.S. Marine Corps
San Pietro (1945), Let There Be Light (1945 completed/1980 released), John Huston
Blood of the Beasts (1949), Georges Franju
Les Statues meurent aussi (1953), Alain Resnais and Chris Marker
India (1958), Roberto Rossellini
Come Back Africa (1959), Lionel Rogosin
Primary (1960), The Chair (1962), Crisis (1963), Robert Drew, Gregory Shuker, Richard Leacock, D.A. Pennebaker
The Exiles (1961), Kent MacKenzie
Lonely Boy (1961), Wolf Koenig
Elgar (1962), Ken Russell
Culloden (1965), Peter Watkins
A Valparaiso (1965), Le Mistral (1966), Joris Ivens
Le Joli Mai (1966), Chris Marker, Pierre Lhomme
Black Natchez (1967), Edward Pincus, David Neuman
A Time for Burning (1967), Barbara Connell, William Jersey
The Anderson Platoon (1967), Pierre Schoendoerffer
Don't Look Back (1967), D.A. Pennebaker
Salesman (1968), Albert Maysles, David Maysles, Charlotte Zwerin
Warredale (1968), Allan King
High School (1969), Frederick Wiseman
A Face of War (1969), Eugene S. Jones
Woodstock (1970), Michael Wadleigh
Gimme Shelter (1970), Albert Maysles, David Maysles, Charlotte Zwerin
The Sorrow and the Pity, A Sense of Loss (1972), Marcel Ophuls
The Resolution (1972 completed/1984 released), Gyula Gazdag, Judit Ember
Phantom India (1972), Louis Malle
The Memory of Justice (1976), Marcel Ophuls
Harlan County USA (1977), Barbara Kopple
The Last Waltz (1978), Martin Scorsese
The Battle of Chile (1978), Patricio Guzman
Gatu of Heaven (1980), Errol Morris
Best Boy (1980), Ira Wohl
Demon Lover Diary (1981), Joel deMott
Middletown: Family Business; Middletown: The Campaign (1982), Tom Cohen
Soldier Girls (1982), Joan Churchill, Nick Broomfield
Mur Murs (1982), Agnes Vardá
Koyaanisqatsi (1983), Ron Fricke and Godfrey Reggio
Kaddish (1985), Steve Brand
Streetwise (1985), Martin Bell
Seventeen (1985), Jeff Kreines, Joel deMott
Bring on the Night (1985), 28 Up (1986), Michael Apted
Stripper (1986), Jerome Gary
Partisans of Vilna (1986), Joshua Waletzky
Routine Pleasures (1986), Jean-Pierre Gorin
Eyes on the Prize (1987), Judith Vecchione (parts 1 and 2), Orlando Bagwell (parts 3 and 5), Callie Crossley and Jane DeVinney (parts 4 and 6), Henry Hampton, Jon Else
Sherman's March (1987), Ross McElwee
Threat (1988), Stefan Jarl
Afghanistan: The Secret War (1988), Mike Hoover, Tim Huntley
Broken Noses (1988), Let's Get Lost (1989), Bruce Weber
Lodz Ghetto (1989), Alan Adelson, Kathryn Taverna
Paris Is Burning (1990), Jenny Livingston (with Barry Swimer)
Tongues Untied (1990), Marlon T. Riggs
The Civil War (1990), Ken Burns
Tale of the Wind (1991), Joris Ivens, Marceline Loridan
Coney Island (1991), The Donner Party (1992), Ric Burns
American Dream (1992), Barbara Kopple (with Cathy Caplan, Tom Haneke, Lawrence Silk)
Black Harvest (1992), Kevin Connolly, Robin Anderson
Silverlake Life: The Viewfrom Here (1993), Tom Joslin, Peter Friedman
Children of Fate (1993), Andrew Young, Susan Todd (with Robert Young, Michael Roemer)
I Am a Promise: The Children of Stanton Elementary School (1993), Susan Raymond, Alan Raymond
Hoop Dreams (1994), Steve James, Frederick Marx, Peter Gilbert (with Gordon Quinn/Kartemquin Films)
Latcho Drum (1994), Tony Gatlif
The Trouble with Evan (1994), When the Bough Breaks (1995), Neil Docherty
Crumb (1995), Terry Zwigoff
High on Crack Street: Lost Lives in Lowell (1995), Jon Alpert, Maryann DiLeo, Richard Farrell
Eternity (1995), Susan MacKinnnon, Lawrence Johnston
The Begging Game (1995), Joel Berlinger, Bruce Sinofsky