I take your point, but, see, there you go. "I gather he's famous in some circles." Blake Shelton isn't famous to you because you don't watch The Voice (at least I assume you don't) or listen to Country Music (I assume you don't do that either, unless there's something you aren't telling us 
).
I do watch TV but I don't watch
The Voice. I actually do listen to country music. Or at least sometimes. Well, OK, not for the past 30 years or so. But I visited Nashville a couple of times in the late '80s and early '90s, went to the Grand Ol' Opry both times (first in the historic original building, then in the new location) and bought a double-album-size CD called
A History of Country Music that I really enjoyed. Its opening song was a scratchy recording of "Turkey in the Straw," then it went all the way through the Carter Family and Hank Williams and Johnny Cash and Dolly Parton and Kris Kristopherson and George Jones and schlocky relatively contemporary guys like Hank Williams Jr. And actually if you count Johnny Cash I have listed to and really enjoyed country music fairly recently.
To people who do both, I'm sure Blake Shelton at least qualifies as A-List and instantly recognizable. (I don't do either, but I do watch TV, so I know who he is. I see him all the time in commercials for The Voice.)
Oh, there's no doubt he's famous. But A-list almost by definition means somebody recognizable to everybody. If you say "Brad Pitt" you don't have to name some movies he's been in for people to understand who you're talking about. Almost everybody has stood in a grocery store checkout line.
I think my guy David Boreanaz is the same deal. To fans of Buffy the Vampire Slayer, and they are legion, or all the folks (like me) who watched him for years on Bones, he is instantly recognizable and I venture A-List to them.
See my point above. For one thing, I totally know who you're talking about. (I wouldn't have recognized his name, but when you say
Bones, I know who you mean.) He's only kind of famous. If he were in a movie, they wouldn't put his name up on the marquee. If the director were trying to cast Jennifer Lawrence in a movie, they wouldn't try to entice her with "David Boreanaz has already signed" (unless she happens to be friends with David Boreanaz, of course).
Compare him to the SMAs of the past. In fact, let's try a little game: Brad. George. Johnny. Tom. Matthew. Chris. David. Ben. Dwayne. Bradley. Ryan. Mel. Hugh. Nick. Channing. Richard. I bet you can guess most of those SMAs of the past by their first name alone. I can see a few that might be slightly more challenging, but once you figure them out you'll go, oh, of course. (Hint: the David on the list isn't David Boreanaz, though the actual SMA David's last name does begin with B.)
And I bet most average Americans, if they were given both first and last names, can at least summon an image of just about every SMA ever. I mean, I don't watch soccer, but I would have no trouble with that one. With the possible exception of Adam (I knew who Adam was, but only because when my sons were little they used to listen to Maroon 5.) And now, I guess, Blake. If you said "David Boreanaz," a lot of people would give you a blank look except avid fans of
Buffy and
Bones (who, I realize, are legion, but still).
What I'm saying is, I've come to have the feeling that A-List is in the eye of the beholder, or at least depends on the perspective of the beholder.
Well, then maybe the SMA should come from the A+ List.
