OK, so Elvis Presley is “The King of Rock-n-Roll”. But we often hear of certain other musical acts being referred to as "The Kings(s) of - " a particular subgenre, such as Michael Jackson being The King Of Pop and so on.
I can think of any number of others, but I’ll let y’all have the fun of listing and debating them.
B. B. King, Albert King or Freddie King (pick the one you like best) - The King of the Blues Guitar
Dick Dale - The King of the Surf Guitar
Jim Morrison - The Lizard King (just kidding here ;))
Too late to edit: We shouldn’t neglect the female royalty:
Aretha Franklin - The Queen of Soul.
Ozzy Osbourne is the Godfather of Metal. Does that count?
Manowar are the Kings of Metal!
This isn’t rock, far from it, but…
Frankie Yankovic has always been the Polka King
And Johannes Strauss was the Waltz King.
And Robert Johnson was King of the Delta Blues.
No. He’s the Prince of Fucking Darkness. Get it right, man. 
Of course, Clapton, Jimi, and Lemmy are all God.
Errr…No. Tony Iommi created the heavy metal sound pioneered by Black Sabbath and Ozzy did a good job as the vocalist. So Tony gets my vote.
But Michael Jackson the king of pop?? Puhleese. That was his own marketing fluff which he never deserved, talented though he was.
As for king of the electric guitar, we’ll never agree. Jimi for me, but Clapton a respectable second. Today Joe Satriani is da man.
The Duke of Earl?
The Count of Basie?
The Duke of Ellington?
(kudos to Bugs Bunny)
**Prince **is His Royal Badness.
Bessie Smith was the Empress of the Blues
Billie Holliday was Lady Day
Solomon Burke was the King of Rock and Soul
ETA: And **Ziggy Stardust **was the Leper Messiah…and **Bowie **the Thin White Duke
And Sinatra was the Chairman of the Board.
Plus, there’s this one guy people call the Boss.
And simply The Voice.
John Philip Sousa was the March King.
James Brown - The Godfather of Soul
Neil Young is Grandpa Grunge. Does that count?
King of Rockabilly Carl Perkins
Queen of Rockabilly Wanda Jackson
Carol King was the Queen of pop songwriters and had a royal Tapestry.
Sting is the King of Pain. And Ray Davies is the King of Kinks.
Would Freddie Mercury be the Queen of Queen?
Actually, besides Presley and Michael Jackson, I’m drawing a blank on other artists being commonly referred to as “King” of any subgenre of rock.
Going in the direction of the other posters… in jazz, Lester Young was the President (later just “Prez”), and Nat Cole was King. (A lot of people think of Cole as a pop singer, but before that, he was one of the great stride pianists of jazz, influencing such people as Art Tatum and Oscar Peterson. He didn’t get the moniker “King” just because his last name was Cole.)
Louie Louie was the Kingsmen.
Crap. I was going to correct you, changing your “was” to “is”, but I searched first and found out you are correct. He died October 10, 2010. Bummer. 