Associated Press added, "This Is It" premiered to high praise from fans who applauded at each number as though they were at a concert and marveled as the singer stepped nimbly through his moonwalk and other signature moves.
Jackson, 50 when he died last June, kept pace with backup dancers half his age during rehearsals for such hits as "Thriller," "Billie Jean," "Beat It" and "Human Nature." The film was shot as Jackson prepared for a marathon concert stand in London that never happened.
Four of Jackson's brothers — Jermaine, Marlon, Tito and Jackie — attended, saying afterward that seeing their brother on film filled them with love and pride.
The movie was pieced together from 100 hours of footage shot at rehearsals for the star's ill-fated comeback shows.
Fan Darryn Wade, in Los Angeles, said: "Judging by that film, it would have been the best show of all time."
But Kasian Daley, 17, at the London premiere, said: "It's an easy way for them to make money off his name."
And Mustapha Duggash, 18, from Nigeria, also at the London screening, said: "I believe it's a nice tribute but the main motivation is the money."
At that premiere, fan Ed Rahmen said the movie proved the concerts at London's O2 Arena would have been "the best thing he had ever done".
David Montalvo, who saw the film in New York, said: "I loved seeing him in action again. It's like you were able to see Michael again for the last time, so it was a good chance to say goodbye to him."
Marilyn Morrison, also in New York, said the footage was "excellent".
She added: "Just seeing all the moves, his original moves, just seeing him doing them again. Just wonderful."
In London, stars including Peter Andre, Spice Girl Mel B and boy band JLS attended the screening at Leicester Square.
Rapper Chipmunk said the film was "absolutely amazing".
He added: "It's given me the package of what his tour could have been if he was still alive."
Some fans protested outside the screenings, saying the film covers up Jackson's declining health.
The dedicated fans, who have set up a campaign called This Is Not It, are accusing concert promoter AEG Live of putting too much pressure on the star during the build up to his 50-date run at London's O2 Arena.
A spokesman for AEG declined to comment.
Jackson, who died on June 25 aged 50, had spent the previous four months rehearsing in Los Angeles.
More than 800,000 tickets had been sold for the concerts, with organisers promising one of the "most expensive and technically advanced" live shows ever.