The best singer-songwriter is in fact Kevin Gilbert. But he ventured more into Prog than the guys you mentioned. He was also far and away the greatest lyricist of all time. Although I'm afraid he was more an atheist than a Jewish person, but a lot of jews have very strange atheistic leanings. Harold Bloom, for example. Here is youtubery of his one of KG's accessible songs:
As for Cohen, past Songs of, I've not really liked it. Stuff probably deserves more listens. In fact, today I was in a Borders and picked up a book of his poetry. I was going to buy it, but I had to take a shit so I didn't.
Rest of the guys you mentioned I'm not a huge fan, I used to like Bob Dylan more but then I watched an interview with him and lost all respect for the guy. I really like Nick Drake and Jeff Buckley, those guys were probably jewish.
