A comment on a post by Rob MacKenzie (and the comment on that post by Ben Wilkinson):
I'm teaching a course on poetry and songwriting right now, and many of the students are in bands (and though they are Swiss, they sing in English). Reading their texts, I am very conscious of the distinction between songs and poems: songs, as Ben put it so well, "lack the singularity that the good poem possesses."
This is a matter of phrasing: writing that can work well in songs often falls flat if read without music, because the presence of the music allows the songwriter to prop up phrases that are unable to stand on their own (too cliched, for example).
That said, I'll defend Dylan (and Tom Waits) as contemporary songwriters who have written many texts that stand up on the page, without the music.