Other than the obvious difficulties one would have in answering the thread-title question, I posit that it's a matter of how we hear, listen and 'see' what the singer is about.

For example, I think Kendall is a 'best' singer. I really think he has the best sense of 'timing' and 'phrasing' in the music business. His ability to get a song across is quite outstanding. (His sense of humour on the other hand . . .).

to be continued