It was hard to tell which group attracted more fans to the concert, which gave equal billing to '80s studs New Kids on the Block (Donnie Wahlberg, 41; Danny Wood, 42; Joey McIntyre, 38; Jordan Knight, 41; Jonathan Knight, 42) and '90s heartthrobs Backstreet Boys (Brian Littrell, 36; Nick Carter, 31; A.J. McLean, 33; Howie Dorough, 37). The fifth BSB Kevin Richardson no longer performs with the group.
Nearly every person in the female-dominated, packed arena danced, howled, and clicked dozens of photos throughout the two-and-a-half-hour show, during which the two groups would switch on stage every five or six songs.
Twenty-somethings wore T-shirts declaring their love for the BSB in puffy paint, and 30-somethings held "I heart Danny" and "Praise the Jord" signs. A group of fans waved "Get naked" signs at whichever group was currently on stage.
The show opened with a medley of NKOTB's "Single" and BSB's "The One" arranged to the melody of Coldplay's "Viva La Vida."
The guys were dressed in dark clothes, wearing the suit jackets, sleeveless vests or T-shirts befitting their parts as the bad boy, hunk or goofball of the group.
The first song had all the quintessential boy-band qualities: synchronized choreography, spotlighted solos and tight harmonies - elements that held true for the entire show.
It also highlighted the extreme entertainment value of the set, giving fans a taste of the fireworks, fog, air-launched streamers, floor-length runway and two circular hydraulic stages that would punctuate the performances.
The NKOTB took the first set, easing their way onto Nostalgia Road with the 2008 single "Summertime." A few songs later, the Kids were back in 1989, showing off their signature sideways kicks and coordinated pelvic thrusts during "You Got It (The Right Stuff)."
BSB joined the first-generation boy-band for an explosive rendition of "Larger Than Life," the second single of the BSB's 1999 album "Millennium" that sold more than 13 million copies.
Then it was back to the Block for a few ballads.
Jordan Knight started off the slower set with the NKOTB version of the Delfonics' "Didn't I (Blow Your Mind)." While Wahlberg, Wood, McIntyre and Jonathan Knight danced behind mic stands, Jordan walked the length of the runway flexing his on-point falsetto.
Wood got a turn in the spotlight during a mash-up of "Valentine Girl" and "If You Go Away."
And McIntyre closed the set with a stirring a cappella solo at the end of New Kids' '88 breakthrough single "Please Don't Go Girl." The crowd swooned as he crooned the lyrics "Please don't go, girl/You would ruin my whole word." The pitch of the screams amplified with every hip gyration until the air seemed to vibrate.
It was the BSBs' turn to serenade the ladies next. Dressed in white iridescent suits, they started with "Show Me the Meaning of Being Lonely" from "Millennium," followed by "10,000 Promises" from "Backstreet's Back."
"Speaking on behalf of all the guys, I have to say we always love coming to Arizona," Dorough told the crowd. "Arizona has the most beautiful ladies in all the world. I think it's time to bring some Arizona love onstage."
Each member walked into the crowd, taking the hand of an adoring fan and leading her onstage. After receiving a long-stemmed rose, the women sat on stools as the boys sang them "I'll Never Break Your Heart" on bended knee.
The NKOTB returned with one of their best-selling singles, "Step by Step." During the electric guitar-heavy rendition of "Cover Girl," Wahlberg enraptured fans by showing off his (better-than-ever) washboard abs after ripping off his black tank top Hulk Hogan-style.
McIntyre relaxed the audience, taking them from the Wahlberg-inspired "Whoo" to more of an "Aww" with a sentimental speech:
"It sort of feels like there's two generations in the house tonight. For some of us, it feels like it's 1989 all over again. For some, it feels like it's 1999 again. Whatever year it is, it feels like magic."
Then, like magic, the BSB appeared on the stairs at the top of the arena's first level singing "Shape of My Heart." Fans rushed nearer to the aisles, jumping over seats with their cameras and reaching over one another to touch the singers.
Once they reached the stage, they progressed through several hits, including "All I Have to Give" and "Quit Playing Games (With My Heart)."
The show ended like it started: with both groups onstage and plenty of pyrotechnics. Representing their hometowns, the NKOTB sported Boston Celtics jerseys while the BSB wore Orlando Magic jerseys as they sang a medley of "Everybody (Backstreet's Back)" and "Hangin' Tough."
Glendale native Jordin Sparks, the 2007 "American Idol" winner, opened the show. Sparks, now 21, seems to be over any of the shyness she had as a teen performer, dancing with attitude and belting out vocals with ease.
"It's been awhile since I've been here," she said. "My family and friends are all here . . . I'm excited to be back. Thanks for all the support over the last five years."
She also had the look of a diva, wearing a glittery purple fringe dress and her hair in a mess of curls reminiscent of a young Janet Jackson.
Sparks performed with two male dancers, and sang six songs, including "No Air," "Tattoo," "Battlefield" and her latest single "I Am Woman."