I wrote about "rock poetry" a few years ago, with no success - not even I understand just what my position was at the time. I'd like to make a quick observation on the matter now that some time has passed. My stance now is strongly inspired by Christgau's: namely, that the function of lyrics is rather different than that of a poem, as the latter is meant to be read, the former to be sung. Good lyrics can often seem unusually flat when quoted, the words themselves sans musical context somehow seeming not as bright as when heard. Their general inability to translate strongly to the pure page shouldn't be taken as a negative pronouncement on the form, I think: it's just that lyrics (obviously) rely on their medium to convey emotion, and so comparisons to classical poetry are unfair. I understand what people mean when they call gifted songwriters "poets" - the meaning of the word has somewhat shifted I suppose - but taking it too literally can lead to confusion and crises of confidence (I speak from experience!). It's a different form, and has different methods of making you feel something. So, assessing the worth of a songwriter is necessarily more complex than simply comparing his writing to that of poets past - for there are few who could rise to such a challenge.
As always, this view is subject to change as well, but the issue was bothering me for a while now. I never knew mimicking Christgau was such an easy option!