This thread was a decent read though. It's clear several of you have not grasped the fact that you can sell millions of record, but that doesn't mean your contributions to the art earn you a title.
1. The dragging of JT.

He's not taken seriously in the R&B genre, as much as his fans try to make him fit in. He's basically a wigger, if you will, and spare me the WPs. There's a reason why Robin Thicke is supported by true fans of the genre rather than JT. He has a few R&B influenced songs, but he's a pop artist at the core. He didn't build his career on making R&B music, therefore he is no way an R&B act. If you asked him what are his favorite R&B albums/artists from yesteryear, I highly doubt he could name more than 5 for each. Who are his influences? Certainly not ppl like James, Stevie, Marvin, etc. True R&B artists. He uses the R&B audience. When Lou Pearlman found out Black folks liked "Gone", he shuffled N'Sync on 106th & Park (a station that caters to Black youth) in order to gain support.
"See right thru you like you bathe in Windex...."
2. Mariah, Mariah, Mariah - she does have R&B styling, but much like Justin, she's a pop artist who does R&B. She, too, did not build a career on the back of R&B music. Her biggest hits are Pop, none of her albums are present on lists ranked by true supporters of the genre (Vibe, BET, Essence, etc). She's hardly a factor in R&B, because none of her music is artistically risk-taking or innovative, there's no way she's the queen of R&B, or any genre for that reason. You don't earn titles by playing it safe.
"Well behaved women seldom make history."
3. Usher - quite possibly the most successful male artist to have practically no impact. A Celine Dion mess. He has inspired a few clones - Chris, Jason D, Omarion, etc - but his actually musical contributions to the genre are next to nothing. Some of you are letting Soundscan numbers cloud your perception of reality. Sure
Confessions was huge, but that album did absolutely nothing for the sound of R&B. Nothing about it, sonically or lyrically was innovative or progressive. He's much like Mariah in that aspect, huge numbers - little impact.
If you're going on the last 20 years, the only contenders for the queen are Janet and Mary J. Blige.
The Velvet Rope,
janet.,
What's The 411?, and
My Life are more transcendent albums than anything put out by any R&B or "R&B" act, and have directly inspired albums by your fave, and those within the genre.
As for king, it's R. Kelly. Nobody else comes close.