Millsaps was in Villopoto's shadow from the time he passed Dungey on the second lap, but could never quite reel in the series champion in front of the largest crowd in the event's nine-year history in Salt Lake City, some 43,149.
"I did the best I could," Millsaps said. "Second is good, for tonight."
It was Villopoto's ninth win of the season, clinching the fifth Supercross title of his spectacular career.
"It's unreal," he said. "It is unbelievable. ... We had a lot of stepping stones to crawl up. It is amazing."
And it was quite likely the last AMA Supercross event in Salt Lake City in the foreseeable future, despite the record crowd. The tour will release its 2014 schedule on Friday, and SLC is not on it.
Supercross was here for four years from 2001-2004, then returned in 2009 for a five-year run that ended with Villopoto on the victory stand. An outdoor motocross event will be held at Miller Motorsports Park on Aug. 17, and Villopoto and his closest competitors Saturday night should be there.
"Ryan rode a great series," Dungey said. "He's a champion, and he showed it again this year."
Jason Anderson of Edgewood, N.M., aboard a Suzuki RM-Z250, took the drama out of the 250 main event, passing Zach Osborne on the second lap and cruising to the win, his first in the series.
"It was actually easier than I thought it would be," Anderson said.
Anderson finished second to Eli Tomac of Cortez, Colo., last year, his first podium finish.
"Utah gives me some good vibes, I guess," he said, noting that it would be a "bummer" if Utah loses its Supercross event.
Actually, the most drama in the 250 class came before the main event.
Ken Roczen of Murrieta, Calif. points leader in the 250 class entering Saturday night's event, leading Tomac 163-143 did not even qualify for the main 250 race, and left the event without any points. He was part of a pileup at the start of the 250 second-chance qualifier, and battled back to close in on the top two who would move on, Travis Baker and Topher Ingalls, but couldn't quite catch Ingalls.
With the chance to move into first in the series with just one race left next week at Las Vegas Tomac didn't capitalize as much as he could have, and finished in sixth place. Roczen now has a five-point lead, 163-158, heading into Las Vegas.
The night started off with a bang. In the first 250 heat, David Pulley of Corona, Calif., went end-over-end off one of the smaller jumps on his Yamaha YZ250F as the crowd gasped and was down for a bit before walking off with assistance.
Storylines Villopoto's wins continue
R Seattle's Ryan Villopoto clinches the Monster Energy AMA Supercross series championship, his third straight.
• Jason Anderson of Edgewood, N.M., wins the Supercross Lites main race, his first-ever victory in the series.