"I don't know what to say. I would have given it to Coldplay," said Brown, who won artist of the year, male pop/rock artist and male soul/R&B artist.
Kanye West, still sore at losing male rap/hip-hop artist last year, won the trophy this time – then said Lil Wayne deserved it more.
"I want to give this award to Wayne," he said. "If it was last year it would have been my award."
It was West's second trophy of the night, following his win for rap/hip-hop album, for Graduation.
"It's our responsibility as musicians to push music to the point it was in the '60s and '70s," he said. "I want to be Elvis."
Host Jimmy Kimmel, who had made West's ego a running joke, quipped: "Elvis died on the toilet with half a jelly doughnut in his mouth. You may want to rethink that."
More WinnersAlicia Keys, who captured two awards for her As I Am album, winning for both the pop/rock and soul/R&B categories, let out a loud "Woooooooo" after picking up a trophy, then dedicated her victory "to all the super women who struggle every day to make it through."
The show climaxed with Keys performing "Superwoman" with Queen Latifah and opera star Kathleen Battle, and ending with a large photo projected on a screen of incoming first lady Michelle Obama.
In a big night for American Idol alums, Daughtry – winner of three trophies last year – picked up another this year for pop/rock group, while former Idol champ Jordin Sparks won for adult contemporary music, and Carrie Underwood won for country album for Carnival Ride.
Taylor Swift, uncomfortably sharing L.A.'s Nokia Theatre auditorium with ex-boyfriend Joe Jonas, won for female country artist, and Rihanna got two awards for pop/rock female artist and female soul R&B artist.
Rascal Flatts picked up their fouth American Music Award – and third in the last three years – for country band, and Brad Paisley won for male country artist, getting a laugh from the audience as he turned over the pyramid-shaped trophy and said, "Made in China?"
Music's A-listers were out in force as the show featured blockbuster performances by Christina Aguilera, Mariah Carey, Beyoncé, Rihanna, West, birthday girl Miley Cyrus and Jonas Brothers, who also won the breakthrough artist award.
And Justin Timberlake made a surprise appearance to introduce award of merit recipient Annie Lennox.
Other winners included:
Linkin Park, alternative rock
Enrique Iglesias, Latin music
Three 6 Mafia, rap/hip-hop group
Third Day, contemporary inspirational music
Alvin and the Chipmunks, soundtrack
Read about more chart-topping musicians!