"Time looked at every song that’s been in the Billboard Top 10 since 1960, the number of hits by each artist present on that list, and how long those musicians’ careers have lasted, and used that information to determine which artists are ultimately the most successful pop-hit generators" (source.)
Rihanna comes in second, Usher in third, Madonna in fifth, Janet Jackson in sixth, Whitney Houston in seventh and Michael Jackson in eighth. Although her albums are not selling like they use to, it's nice to know her achievements still mean something. Click HERE to view this interactive infographic, which shows how other pop stars rank.