In 2014, Sight & Sound polled 340 documentary critics, curators, academics and filmmakers asking for top 10 documentary lists. Over 1000 films got votes, from years as early as 1892 to as recent as 2013. This list is the combined critics and filmmakers list of all films that received 3 or more votes.
Source: http://www.bfi.org.uk/sight-sound-magazine/greatest-docs
In 2015, the Museum of Cinematography in Łódź asked 279 film professionals to vote for the best Polish films of all time. The top 65 films are ranked, all with 12 votes or more. The next 40 films are unranked, with 6-11 votes.
Source: http://kinomuzeum.pl/?p=15020
Short films I have seen
Sight and Sound's The Greatest Documentaries of All Time
by maxwelldeuxVIP 8