Although I don't like the "best" concept, I have enjoyed Joni Mitchell, Richie Havens and of course Bob Dylan, I'm not sure that I saw their names earlier in this thread.

If the question is who is the best we know personally, I give unbiased nod to Susan Latimer. Okay, she's my sister but she has performed at the Mariposa and Eaglewood festivals in Ontario and writes very interesting material founded in her classical training and her exposure to Blues, Celtic and Bluegrass.

Rick mentioned Norm Hacking, I saw him when Susan was performing at the Eaglewood festival a few years ago and was very impressed with him and his material.