How often are going to have this discussion? Good poetry makes for horrible lyrics, and good lyrics make horrible poetry. It's lychees and brake shoes.
Some time back, to make my point, I actually threw John Lennon under the bus because I claimed that the lyrics to Imagine make for an absolutely god-awful poem. And they do. I consider Lennon to be one of the best song writers I know of, and yet I stand by it.
Fantastic lyrics; see also Strawberry Fields, Julia, In My Life, Everybody's Got Something to Hide Except for Me and My Monkey, All You Need is Love...all great tunes with great lyrics that fall completely flat upon recitation.
Now try Dylan; oft-considered to be one of the most "poetic" of lyricists. Try reading Visions of Johanna, A Hard Rain's Gonna Fall, Desolation Row out loud, or even to yourself. It's almost laughable in some cases. I mean "I saw a young girl, she gave me a rainbow." Or "Einstein disguised as Robin Hood, with his memories in a trunk, passed this way an hour ago with his friend, a jeleous monk." Seriously, would any of you ever have the nerve to read that to a room full of people at a poetry reading?
But Dylan can pull it off in a song because, well, he's a song and dance man. That, and because his voice and chordal phrasing can paint an image that mere words cannot. Poetry is words and nothing else. They need to be strong enough to stand on their own merit with no crutch.
So let's not even bring rap into this. I'll have to go find my rusty grapefruit spoon.