What if we consider individual performances of songs. Not careers of singers, but single vocal performances.
Now, let us agree to not, for the exercise, consider technical merits--not tone, not intonation, not color, not control, not power, not range. Not beauty. No taking into consideration how pretty or pure the voice is.
Instead, let us consider solely the phrasing; the way a singer can act a song, from within the music and meter. Still; we are not considering spoken-word, or recited poems, but real songs, sung.
If we do all this and honestly consider some of the greatest vocal performances ever recorded--the performances that, again, speaking purely of non-technical matters, are the most remarkable, the most moving and perfect examples of singing a song in such a way as to move the listener the most, and to tell as specific a story as possible through that music--which performances come to mind? A variety of Dylan and Louis Armstrong? Of course. But the performance that jumps to my mind as one of the all-time most remarkable examples of the art of singing once beauty of voice--that admittedly very important component--is removed from the equation? Kermit the Frog's original, Sesame Street rendition of "It's Not Easy Being Green." Sublime.