You can't really throw in Whitney because she's a different side of the same coin as Janet and Madonna. She's in a league of her own in that aspect.
Janet and Madonna are easily the two most influential women of the past 30 years. Madonna is more popular than Janet, obviously, but Janet's contributions to the art form are just as great as Madonna's, if not more because of the reach.
Edit: Totally did not even answer the question.
Looks: Janet and Whitney are both stunning. Madonna was mildly attractive back in her younger years.
Talent: Whitney and Janet both have God given talents that they perfected. Madonna is a smart businesswoman. So they're all pretty equal in that aspect imo.
Gays: eh, probably Madonna since she appeals to more ppl globally.