i am trying to find some good ones
TOP 50 by vote on IMDb.com
1No Direction Home: Bob Dylan (2005) 8.5/10 (1764 votes)
2Chagrin et la pitié, Le (1969) 8.5/10 (620 votes)
3Nirvana Live! Tonight! Sold Out!! (1994) 8.5/10 (419 votes)
4My Flesh and Blood (2003) 8.5/10 (442 votes)
5Nuit et brouillard (1955) 8.4/10 (1915 votes)
6Times of Harvey Milk, The (1984) 8.4/10 (591 votes)
7Promises (2001) 8.4/10 (627 votes)
8Hearts and Minds (1974) 8.3/10 (650 votes)
9Bowling for Columbine (2002) 8.3/10 (47331 votes)
10Fog of War: Eleven Lessons from the Life of Robert S. McNamara, The (2003) 8.3/10 (5322 votes)
11Nema-ye Nazdik (1990) 8.3/10 (557 votes)
12Chelovek s kino-apparatom (1929) 8.3/10 (1767 votes)
13Ilha das Flores (1989) 8.3/10 (633 votes)
14Corporation, The (2003) 8.2/10 (4231 votes)
15Harlan County, U.S.A. (1976) 8.2/10 (426 votes)
16Olympia 1. Teil - Fest der Völker (1938) 8.2/10 (678 votes)
17Vieuphoria (1994) 8.2/10 (230 votes)
18Zapruder Film of Kennedy Assassination (1963) 8.2/10 (378 votes)
19Waco: The Rules of Engagement (1997) 8.2/10 (710 votes)
20Lektionen in Finsternis (1992) 8.2/10 (372 votes)
21Titicut Follies (1967) 8.1/10 (374 votes)
22Children Underground (2001) 8.1/10 (274 votes)
23Touching the Void (2003) 8.1/10 (5630 votes)
24Berlin: Die Sinfonie der Großstadt (1927) 8.1/10 (398 votes)
25Un coupable idéal (2001) 8.1/10 (579 votes)
26Why We Fight (2005) 8.1/10 (1906 votes)
27Mio viaggio in Italia, Il (1999) 8.1/10 (536 votes)
28Capturing the Friedmans (2003) 8.1/10 (4555 votes)
29Olympia 2. Teil - Fest der Schönheit (1938) 8.1/10 (457 votes)
30Manufacturing Consent: Noam Chomsky and the Media (1992) 8.0/10 (1050 votes)
31Murderball (2005) 8.0/10 (2722 votes)
32Stevie (2002) 8.0/10 (786 votes)
33Grizzly Man (2005) 8.0/10 (5197 votes)
34For All Mankind (1989) 8.0/10 (338 votes)
35Sound and Fury (2000) 8.0/10 (225 votes)
36Pink Floyd: Live at Pompeii (1972) 8.0/10 (1196 votes)
37Macht der Bilder: Leni Riefenstahl, Die (1993) 8.0/10 (461 votes)
38Powers of Ten (1977) 8.0/10 (204 votes)
39Hearts of Darkness: A Filmmaker’s Apocalypse (1991) 8.0/10 (3160 votes)
40Salesman (1969) 8.0/10 (491 votes)
41Sans soleil (1983) 8.0/10 (588 votes)
42Cane Toads (1988) 8.0/10 (321 votes)
43Zendegi va digar hich (1991) 7.9/10 (349 votes)
44Spellbound (2002/I) 7.9/10 (4394 votes)
45Inconvenient Truth, An (2006) 7.9/10 (3556 votes)
46Unprecedented: The 2000 Presidential Election (2002) 7.9/10 (324 votes)
47Peuple migrateur, Le (2001) 7.9/10 (4108 votes)
48Rivers and Tides (2001) 7.9/10 (630 votes)
49Little Dieter Needs to Fly (1997) 7.9/10 (432 votes)
50Death in Gaza (2004) 7.9/10 (338 votes)
I liked these two, but not sure if they are actually Documentray films: My Brother’s Keeper, Story of the Weeping Camel