It seemed to me that the best known recording of Leonard Cohen's "Susanne" in German/Germany was by Hermann von Ween. He is mentioned earlier in this thread and although Dutch and not a folksinger, is an incredible performer.
Bettina Wegner had a passing reference above. "Kinder" is an incredible song but I was really moved by a song which involved the reciting of the names of the various concentration camps.
Hannes Wader's anthologies "Folk Friends" and "Folk Friends 2" are treasure houses of material in German and English. As well as his own songs, he brought a lot of brilliant British and American performers together for the recordings which apparently took place over two weeks at a windmill he owned. One track which stands out for me was "Lonely One" written and performed by Finbar Furey. I don't think anyone who travels and does gigs could fail to relate to it. I've never heard it sung by anyone else which is a pity as it's a very powerful song.
The albums are probably long out of print but if you come across a copy – grab it!

Eddie