Janis Joplin didn’t have a very good voice (in my opinion). But by golly, she sure did have a stage presence. Unforgettable.
I thought her interpretations were unique and valuable.
(But Big Mama Thornton was a lot better; and with Hound Dog, too...)
http://www.youtube.com/watch?v=vbdUjHmCHA4https://www.youtube.com/watch?v=vbdUjHmCHA40
http://www.youtube.com/watch?v=yoHDrzw-RPg
Without stage presence and that certain charisma, you can have the smoothest, most polished voice yet never have a hit song or fill a concert hall. Polished voices are a dime aa dozen.
Bob Dylan is another example of an artist not having a smooth and polished voice, yet he is one of the all-time greatest songwriter/performers.