Louis Armstrong is the unquestioned king of the jazz vocal genre. There really is no one else who comes close in skill, technique and phrasing. The fact that he could achieve all of that with a voice which was not classically beautiful is all the more a testament to his talent. In addition, he was immensely popular. In his time, he was more popular than the Beatles were in theirs.
Bing Crosby and Frank Sinatra are generally considered to be pop singers, not jazz singers.
Among the great jazz crooners, Nat King Cole and Billy Eckstine stand at the top. Other than to us audiophiles, Johnny Hartman made a relatively small impression on the music scene, although his talent is up there with Billy Eckstine and the two of them sound quite similar.
Bing Crosby and Frank Sinatra are generally considered to be pop singers, not jazz singers.
Among the great jazz crooners, Nat King Cole and Billy Eckstine stand at the top. Other than to us audiophiles, Johnny Hartman made a relatively small impression on the music scene, although his talent is up there with Billy Eckstine and the two of them sound quite similar.