As a songwriter about whom some rather excessively nice things have been said, I'm not keen on hyperbole. personally, the last song of Dylan's I liked was "the times they are a changing" but there's a large number of people who will disagree with me. The "best" must be subjective. As writers I put people such as Ewan McColl, Stan Rogers,
and Cyril Tawney high on my list of role models, but I don't have a "best". Has anybody mentioned Australia's John Dengate? His song "Carlingford" still brings me close to tears after about fifteen years of singing it and his poem "The Lanes of Wooloomooloo" is up alongside Kipling in its portrayal of the victims of war.
Folk music, to me is not about competition, it's about singing and the "Best" music to me is that made by forty or so voices making a great chorus work hard.