None of the above. That's a list of "most promoted by the record companies", and, as a result, "most popular". They may or may not have good voices, but as contributors to the world of music? Meh. I notice you did, at least, leave out Lady Gaga and Madonna, hopefully because "tittilatin' the rubes" /= "vocalist".
My list would be substantially different.
In no particular order, Bonnie Raitt, Heather Massey, Ruth Moody, Nicki Mehta and, if you also want a top songwriter, Gillian Welch. Or, if you want someone who can play the shit out of an instrument or two Sara Jarosz or Allison Krause. I also like Kimbra, but that may be coz she got a purty mouth. Also the gorgeous EmmyLou Harris, if only for her f'ing impeccable taste, demonstrated over 40 years (her voice is long gone).
Actually, they can all play, most of them write songs and none of them, not one, has a huge production ensemble with 50 dancers and 90 musicians, or a meat dress. Not one of them has considered musical "success" to be more important than playing the music that moves them, or that they are moved to create.
But hey, to each his own.