Who came before Gaga?

HERSTORY TEST: A bunch of us were sitting around the HITS cesspool the other day trying to come up with recent (meaning in the last decade or so) historical precedents for Lady Gaga as a pop force of this enormity. The names of Beyonce and Justin Timberlake came up, but both sprang out of already mega groups, riding the attendant momentum. Eminem was huge and game-changing, but he crossed over from rap, and the rock arena simply doesn’t hatch superstars as it once did. In the end, there was only one previous latter-day pop superstar on our list—Britney Spears. Have we stupidly overlooked a recent pop colossus? (8/11a)