I think Michael Jackson and Whitney Houston are more 80s than 90s.
Eminem was more of 2000s.
I would rather consider 90s real rappers like 2pac, Coolio, The Notorious B.I.G. Snoop Dogg, Wu-Tang Clan, Will Smith and others.
As for R&B I'll take Jodeci, Boyz II Men, 112, Jagged Edge, Destiny Child, R. Kelly, Brandy, Monica, Toni Braxton, Backstreet, etc.
As I mentioned in the publication, both Michael J and Whitney started in years that preceded the 90's, but without a doubt they left in the 90's and had unforgettable hits, and although Enimen's success was in 2000 she was launched as a singer in 1996, as I pointed out.
As for tastes, we all have different, that's what variety is all about and when talking about solos I could not mention for example Boys II Men or Destiny Child, that would be in another publication of groups as I already did a previous one where I mentioned the BSB, Toni Braxton I remember only one song.