Rihanna was selected by Billboard to be their "Top Pop Artist of the Last 20 Years." The Bajan beauty beat industry veterans including Celine Dion, Mariah Carey, Beyonce, Lady Gaga, Katy Perry, Janet Jackson and even her on-again off-again rumored beau Chris Brown.Just a few days prior to learning the great news, on Oct. 5 Rihanna tweeted the latest campaign ad photo for her newest fragrance, "Nude."