I am a song writer as well. I was even talked into letting some one play and sing one of my songs at my wedding reception. Everyone loved it except me of course since I am sure that everything I write is crap. Some of my best works however start as a poem and then I pick up my guitar and it becomes a song. My opinion is (most) songs are just another form of poetry. So if you can win Nobel Prize for Literature with a poem then I don't see why it can't be recognized. Winning the award may be different but as I am not too familiar with Leonard Cohen's work.