I assume that Paul Papavgeris is too young to remember Robeson and Belafonte. They were, each, in their time, the most popular folksingers in the world. Paul Robeson was a concert performer who presented, and recorded, what were known as Negro spirituals and work songs. His 78's could be found in every folk lover's collection. His classical training and world wide fame separated him from folksingers like Almeda Riddle or Doc Boggs but his songs were, well, within the limits of folk.
Harry Belafonte was, simply, the man who moved folk into the younger and most popular market. He was the first folk teen idol and he accomplished this without sacrificing musical integrity. Known, primarily, for his calypso songs, his concerts and recordings were eclectic and wildly successful. Like Robeson, Belafonte was a wonderful actor. It is interesting that so many folksingers have had acting careers (Burl Ives, Will Geer, Theo Bikel, Alan Arkin, Eartha Kitt).
I fear that these informal polls are more a test of generation. Altes, like me, are locked into our heros and young posters are often unaware of the great talents that shone before they existed. Well, perhaps we can all learn to expand our experiences.