1. Hoop Dreams (1994), directed by Steve James, Peter Gilbert and Frederick Marx
2. The Thin Blue Line (1988),directed by Errol Morris
3. Bowling for Columbine (2002), directed by Michael Moore
4. Spellbound (2002), directed by Jeffery Blitz
5. Harlan County U.S.A. (1976), directed by Barbara Kopple
6. An Inconvenient Truth (2006), directed by Davis Guggenheim
7. Crumb (1994), directed by Terry Zwigoff’s Crumb
8. Gimme Shelter (1970),directed by Albert and David Maysles and Charlotte Zwerin
9. The Fog of War (2003), directed by Errol Morris
10. Roger and Me (1989), directed by Michael Moore
11. Super Size Me (2004), directed by Morgan Spurlock
12. Don’t Look Back (1967), directed by DA Pennebaker
13. Salesman (1968), directed by Albert and David Maysles
14. Koyaanisqatsi (1982), directed by Godfrey Reggio
15. Sherman’s March (1986), directed by Ross McElwee
16. Grey Gardens (1975), directed by Albert and David Maysles, Ellen Hovde and Muffie Meyer
17. Capturing the Friedmans (2003), directed by Andrew Jarecki
18. Born into Brothels (2004), directed by Ross Kauffman and Zana Briski
19. Titticut Follies (1967), directed by Frederick Wiseman
20. Buena Vista Social Club (1999), directed by Wim Wenders
21. Fahrenheit 9/11 (2004), directed by Michael Moore
22. Winged Migration (2001), directed by Jacques Perrin
23. Grizzly Man (2005), directed by Werner Herzog
24. Night and Fog (1955), directed by Alain Resnais
25. Woodstock (1970), directed by Michael Wadleigh

I’ve seen 20 of the films from this list. But my favourite doc wasn’t mentioned and that is Fast, Cheap & Out of Control by Errol Morris.