In September 2008, it was announced that Aguilera would release a greatest hits album titled Keeps Gettin' Better: A Decade of Hits, whose distribution rights in the United States belonged to Target retailer via her record label RCA Records. On the compilation's title, Aguilera said: "I'm looking forward to the next 10 years, which is partly why I named the album, Keeps Gettin' Better, 'cause it does". People who pre-ordered the compilation would receive a free digital download version of the single "Keeps Gettin' Better". During an interview with the Los Angeles Times, Aguilera explained that Target "got such a great creative team", and that's why she worked with the retailer for the album. Released in November 2008, Keeps Gettin' Better: A Decade of Hits features all of Aguilera's hits from her previous studio albums released up to 2008 and four new songs produced by Linda Perry. Two of which are remakes of her previous singles, "Genie 2.0" ("Genie in a Bottle"), and "You Are What You Are (Beautiful)" ("Beautiful"). The other new songs were "Keeps Gettin' Better" and "Dynamite". The new material is inspired by electropop, which was deemed as Lady Gaga-influenced by a reviewer from Rolling Stone.
Keeps Gettin' Better: A Decade of Hits received generally positive reviews from music critics. AllMusic writer Stephen Thomas Erlewine commented that the compilation "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." Nick Levine from Digital Spy noted the "spunky attitude" of the compilation and compared her recordings to those of Britney Spears: "She may have started out with similar material to another Mickey Mouse Club alumnus, but Aguilera moved on to bigger and better things more quickly than Britney." He further complimented on Aguilera's songwriting skills.
Chris Willman from Entertainment Weekly noted the lack of traditional Aguilera styles on the new songs, stating: "The singer has banished melisma and belting from these electronic confections, and her chops sound just as hot set on simmer." Writing for Sputnikmusic, Nick Butler positively reviewed Aguilera's new material, saying: "Christina the pop singer is dead, long live Electro Christina [...] At any rate, these four tracks are more than enough to build anticipation for what could be a very, very good album." In a mixed review, an editor from Rolling Stone shared that Keeps Gettin' Better: A Decade of Hits was "weighed down by four bland attempts at 2008's trendy, Lady Gaga-jacking electropop."
In the United States, Keeps Gettin' Better: A Decade of Hits debuted at number nine on the US Billboard 200 on the issue date of November 29, 2008, selling 73,000 copies in its first week of release. The album spent six weeks on the Top Catalog Albums, where it peaked at number 2 in 2010. As of September 2014, the greatest hits album has sold over 530,000 copies, according to data compiled by Nielsen SoundScan. In Canada, the album charted at number twelve on the Canadian Albums Chart.
In Australia, Keeps Gettin' Better: A Decade of Hits peaked at number eight on the ARIA Albums Chart on the issue date of November 23, 2008 and spent nine weeks on the chart. In Austria, the album debuted at number ten on the Austrian Albums Chart on the issue date of November 21, 2008 and remained on the chart for five weeks. The album also experienced moderate success in various European regions, including France (number seven), Ireland and Finland (number nine), and the United Kingdom (number ten). In 2008, Keeps Gettin' Better sold 19,030 physical copies and 250 digital units in France.