Bob Dylan, as a vocalist, is hugely important. First of all, his rhythmic delivery is awesome. Listen to "Like a Rolling Stone", for example, where his singing is easily the most powerful timekeeper in the group. Also, the melodic contours that he finds are not the usual ones. Try singing "It's All Over Now, Baby Blue", and you'll see what I'm getting at. Third, he makes us consider what we are getting from listening to a singer. For instance, many people who see him in concert are astonished at how he changes the phrasing and melodies of his songs, almost to the point where they are unrecognizable - one of the main reasons that he does so is a simple one: he doesn't want the crowd singing along with him. And finally, in terms of influence, leaving aside the obvious examples (virtually any "singer-songwriter"), the rockers Lou Reed, Ian Hunter and Bryan Ferry are directly and deeply in his debt as vocalists. Listen to "Prominent Men", "Sweet Angeline", and "Virginia Plain" for evidence. I don't know about you, but I don't even want to imagine a world without The Velvet Underground, Mott the Hoople, and Roxy Music. Could these groups have existed without Dylan? The answer, my friend... (Suggested listening: "Queen Jane Approximately")