Question: Who had the most hits in the 90s?
Disambiguated questions and answers: question: Who had the most hits in the 90s in baseball?
Who had the highest number of top hits on the top 100 Billboard charts in the 1990s?
answer: Mark Grace
Mariah Carey
Natural Questions answer: Mariah Carey (from the Wikipedia article "List of Billboard Hot 100 chart achievements by decade")