With today's release of Britney Spears new album, Femme Fatale, we're looking back in time at the artists who would sing and dance their way into becoming household names. From Diana Ross to Lady Gaga, these acts had that X-factor that set standards for all of their contemporaries. It can mean talent, shock value, personality, a cult following, and more. Yet, that X-factor doesn't necessarily mean attractiveness. Only a lucky few can be regarded as the hottest artists throughout time. Sure, appeal is relative, but there have been those women whom teenage boys and even grown men feel no shame about posting on their wall (Facebook or actual room). Today, we're counting down the undeniably hottest women throughout pop music history.