Who was the 2nd biggest artist in the Michael Jackson era?

We all know MJ ruled the 80s and the 90s and was by far and the way not only the most popular artist in the world but the most popular person in the world but during MJ reign who was the 2nd most popular?

Was it Madonna who is the best selling female artist ever and often referred to as “The Queen Of Pop” or the musical genius who could practically play any instrument and his biggest musical rival Prince?