The 19-year-old pop music sweetheart took the show's top award Sunday night as she did at the Country Music Awards earlier this month, giving Jackson his only loss of the night, and giving her five trophies in all.
"Music has never been ultimately about competition," she said as she accepted the top prize via satellite from London, where she is to perform Monday. "To even be mentioned in a category with Michael Jackson, who we will miss and love forever, is an unimaginable honor."
Swift was also named favorite female pop/rock and country artist and favorite adult-contemporary artist. Her album, "Fearless," won favorite country album.
Jackson was honored with four American Music, making history by collecting more AMAs - 23- during his career than any other artist and becoming the show's winningest posthumous artist.
Jackson was nominated for five awards, just one shy of nominee leader Taylor Swift. He was named favorite male artist in the pop/rock and soul/R&B categories. His 2003 greatest-hits album, ``Number Ones,'' also won favorite album in both categories.
These were accepted by his brother Jermaine Jackson, wearing a glittering white glove in his brother's honor.
He thanked "Allah for blessing my entire family" and named each of his brothers and sisters. He said Michael's message is more important than any award.
"`The message that Michael had will live on forever," he said. "He saw good in everyone and he wanted everyone to do good. He always started with love."
The group Gloriana was named breakthrough artist of the year.
Among the winners was the band Green Day won for best alternative rock; singer Beyonce for best female soul/R&B artist; singer Keith Urban for best male country star; the Black Eyed Peas for best pop/rock band; and Rascal Flatts for best country group.
The American Music Awards honor the year's top-selling artists in the categories of pop/rock, country, rap/hip-hop, soul/R&B, alternative, adult contemporary, Latin and contemporary inspirational. Fans voted online to select the winners.
But it was the performances that stood out during Sunday's show that closed with an S&M-themed, sexually charged performance by Adam Lambert (which included him shoving a male dancer's face into his crotch).
It also featured a jaw-dropping performance from Lady Gaga, who literally set the stage on fire.
Wearing a Vulcan-inspired headdress and vest filled with lights, she performed songs from her new album, "The Fame Monster," due in stores next week. She used her microphone to break into a glass case, where a grand piano sat waiting. It caught fire when she sat down to play.
Janet Jackson kicked off ceremony with a medley of some of her biggest hits. Jackson's performance didn't acknowledge her late brother, as she did at the MTV Video Music Awards, but it did remind fans of her own long career, and perhaps of her just-released greatest-hits album, "Number Ones."
Whitney Houston made a resplendent return to the AMA stage with an elegant performance of "I Didn't Know My Own Strength." The 46-year-old entertainer also received the International Award of Excellence for her musical and philanthropic contributions. She dedicated the honor to her daughter, music mogul Clive Davis and "everybody who supported me."
The Black Eyed Peas, voted favorite pop/rock band, energized the crowd when they performed two of the year's most popular hits: "I Got A Feeling" and "Boom Boom Pow."
Rihanna returned to the AMA stage, sporting blonde hair, a skintight, white peek-a-boo bodysuit and a tattoo down the front of her neck that read "Rated R," the name of her new album, out this week.
Alicia Keys and Jay-Z dueted on their ode to New York City, "Empire State Of Mind."
Shakira was flanked by a dozen dancers in tiny black bodysuits as she sang her new single. Kelly Clarkson performed a stripped down version of her hit "Already Gone," backed by a string quartet.
Jennifer Lopez added a boxing motif to her dance-filled performance, but she slipped during a tricky move and landed on her bottom.
Green Day lead singer Billie Joe Armstrong confessed backstage that the show left him star-struck.
"When you see all the talent that's in the room" like Jay-Z and Lady Gaga, he said, "it's like holy moly, these are huge people."
The band was voted favorite alternative artist. Other winners Sunday included Jay-Z, his wife Beyonce, and Rascal Flatts.