Dylan is the best that I have ever heard. Willie Nelson, Hank Williams, The Glimmer Twins, Lennon & McCartney (let's not forget George Harrison's contributions) have all been mentioned here but I would include them on my list. Let's not forget the other Willie, Willie Dixon who wrote so many of the Chicago Blues classics that were recorded by Muddy, Howlin Wolf, Little Walter etc. Robert Johnson
seems to be absent from this list. I'm surprised that Bill Monroe hasn't been mentioned yet. Carter and Ralph Stanley wrote some beauties.