Pink Floyd

Not only singers (female or male), actors or celebrities are compared with Madonnah. Even the Mundial's opening ceremony in 2014 was compared by professional journalists her fans with this unoriginal, uncreative copycat who didn't push any boundary. Her so called "reinventions" are nothing but rip offs from one person to another. She copies everyone from singers, actresses, poets through painters, movie directors to choreogrphers and composers. 
On the left photos we see a huge, automatically opened disco ball from 2006 "future thiefs" on confessions tour. Pink Floyd copied that idea from Madge and backed into time to 1994.

Whitney Houston

I sincerely believe that if Whitney Huston had hit it big in the late 90s and not the late 80s that she'd be alive today. The racist US media cared only about Madonna and Whitney never ever received the magazine covers (not one mainstream cover), press coverage and critical due that she deserved. Despite achieving the top TWO FILMS in two years (making her the number one female box office star for that period which Madonna will never accomplish) and selling 40+ million albums in a few years she was considered niche because of her race. There were no Beyonces or Black female, wholesome household names until Whitney yet as the first she was treated somewhat like a freak by the Madonnacentric media. Madonna exploited this fact and used it to her advantage with the media's full support and backing. Had Whitney had a powerful platform in the media like Beyonce and Rihanna do today I believe she would not have drifted into deadly excess.