When Christina Aguilera began her decade of hits back in 1999 she was instantly overshadowed by her fellow New Mickey Mouse Club alumni Britney Spears, who was first out of the gate with Baby One More Time and wound up outselling Christina and every other teen pop act this side of *NSync in the first years of the new millennium. As the 2000s rolled on, Aguilera slowly, surely began to eclipse Spears. Brit-Brit’s downward spiral and arrested artistic development seemed all the stronger when compared to Xtina’s restless risks and increasingly assured musical vision, a progression that’s evident on Keeps Gettin’ Better: A Decade of Hits. Arranged chronologically from 1999′s “Genie in a Bottle” to 2007′s “Candyman,” Keeps Gettin’ Better has a narrative momentum: the squeaky-clean pop singer shatters her image via hyper-sexualized dance tracks which left her free to get crazier, campier, and better, turning into a pop diva that truly deserves that title. Keeps Gettin’ Better hints at the future with two excellent new songs (the title track and “Dynamite”) along with remakes of “Genie in a Bottle” and “Beautiful,”" all done in a chilly electro style that suggests a Blackout if Britney were in control and knew what she was doing, but what is remarkable about the collection is that Christina’s past holds up, with the candy-pop of “Genie,” “What a Girl Wants,” and “Come on Over Baby (All I Want Is You)” still sounding sweet, “Beautiful” sounding richly melancholy, and “Ain’t No Other Man” and “Candyman” wickedly funny, knowing blasts of retro-swing. She may have started out in Britney’s shadow, but Keeps Gettin’ Better proves that no other teen pop singer of her era has a better track record than Christina and if the new songs are any indication, the title of this hits comp is no lie either. – Stephen Thomas Erlewine