"Fifty-one years ago, he was born into the world," said Lee, who directed the "They Don't Care About Us" music video for Jackson in 1996.
"I'm like everybody else - somebody who loved his talent," he said. "We're here to celebrate Michael Jackson."
Several thousand dancers packed themselves close together on the muddy Prospect Park grass facing a huge stage. Deejays played Jackson's music spanning his whole career - from his childhood with "The Jackson 5" to his final tracks.
There was a giant white birthday cake that read "Happy Birthday Michael Jackson" in red frosting. Balloons dotted the sky.
The biggest cheers came late in the day when the deejay played one of Jackson's best known hits, "Beat It."
"I don't even remember life without him," actor/comedian "Tracy Morgan" said at Saturday's party. "Michael Jackson was everything."
Brooklyn City Council Woman Lettitia James last week suggested adding "Jackson" to the Hoyt-Schermerhorn subway station's name. The station served as an iconic backdrop for the 1987 music video of "Bad."