Comparison with other singers and writers is pointless - Dylan was and is unique.
Criticisms of the technical quality of his voice are also pointless - many of the singers who have "good" voices are very often as boring as hell. Dylan is rarely boring.
The magic element is probably that the whole mix of songs, voice, music, delivery and pertinence to us and our times just happen to come together in the right way.
Another thing I find paradoxical is that someone so downbeat and understated can be so charismatic - the man has an aura about him, especially live, but even on TV as well. I still keep telling myself how lucky I am to have grown up in the Dylan era.