The film, a blistering indictment of US President George W. Bush that makes no attempt at neutrality, last weekend became the first documentary in history to rake in more than 100 million dollars in North American ticket sales.
"Before, you couldn't convince exhibitors that there was an audience for non fiction films," Moore said. "Now the challenge is on myself and other filmmakers to continue making things for this audience."
Moore's polemic won the coveted Palme d'Or prize at this year's Cannes Film Festival, and has sold 103 million dollars in tickets in the United States and Canada since its release in late June. The previous record holder - Oscar-winning "Bowling for Columbine," another Moore brainchild - took in 21.6 million dollars.
"I can't recall the last time we've seen a documentary getting this attention. No documentary has ever achieved the status of a mainstream film, a feature," said industry analyst Tom O'Neil.
The film, which offers an unflattering portrayal of the president's reaction to the September 11, 2001 terrorist attacks and the subsequent war in Iraq, has become part of the national debate ahead of the November 2 presidential election.
At the request of local peace activists, "Fahrenheit" was screened in tiny Crawford, Texas on Wednesday, just miles from where the president was spending the week on his 1,600-acre (850-hectare) ranch. Moore invited Bush to the screening, prompting laughs from the White House.
Moore meanwhile was at the Democratic National Convention in Boston, Massachusetts, where he was a prominent if unofficial participant. He has undeniably helped attract moviegoers to a medium often more educational than entertaining. This year, 45 documentaries are being screened commercially in the United States and Canada, 16 more than the previous year and 17 more than in 2002, according to Nielsen EDI.
"There has been an extraordinary transformation," Geoff Gilmore, chief of programming for the Sundance Film Festival, told USA Today. "The documentaries sold out this year so quickly at the Festival, we had to add screenings. "For years they were stigmatised as talking heads you had to see in school. Now look at the tremendous rage out there."
Another documentary making waves this year is "Supersize Me," by former MTV presenter Morgan Spurlock. The gross-out look at American fast-food sold 10.9 million dollars worth of tickets, putting it at number three on the list of most-seen documentaries.
During the one month shooting of the film - it cost just 65,000 dollars to make - Spurlock ate only at McDonald's. The result: he gained 12 kilograms (26 pounds), his cholesterol levels shot up and doctors following the experiment ultimately told him to drop it when he began developing liver problems.
Another high-profile documentary this year was "Touching the Void," based on the international best-seller of the same name, directed by Kevin Macdonald. The mountain climber thriller sold 4.6 million dollars in tickets, putting it at number eight on the list of top documentaries.
"This clearly shows that Americans want to see films that show real life, that they need more provoking material," Marty Kaplan of the University of Southern California told AFP. "Also the quality of documentaries has tremendously improved in the past years."
Clearly, too, they offer more food for thought than blockbusters like "Spiderman 2" and "Shrek 2."
"I think it is going to be the first documentary to be nominated and to win best picture at the Oscars," O'Neil, an expert on cinema and television awards, told AFP.
"I don't think Bush will be nominated for best actor," he quipped.