Well, Janet had the Superbowl which destroyed her relevancy, but Madonna is way older and has a longer career. Radio played her when she was 40 (
Ray Of Light/
Music eras), and it's not like Mariah's latest album wasn't a complete bomb.
And, obviously, Madonna is still 10 times more successful than Mariah on a worldwide scale. Not to talk about touring. Madonna had a way more successful decade than Mariah.