ddw -- I'm sure that "Watchtower" is the *best-selling* Dylan cover, thanks to the huge sales of Jimi's great reinterpretation. However,I'm not sure that very many other artists have recorded their own versions. Of course, if you count performances rather than recordings, countless semi-pro rock bands play the song every weekend.

Assuming it is correct that "Farewell" was once covered by more different recording artists than any other Dylan song, it probably still merits that distinction -- I would guess...