In terms of Art Song and human expression and feelings, I think probably Schubert, Wolf and Richard Strauss are probably in a higher league than Brel. I'm not sure that you don't do them a disservice in saying that he is probably the greatest ever. However you need singers with better voices than you find in your usual folk club to get the best out of their songs! Also a fluency in German. As to snobbery I do believe that there some performers who see themselves as elitist and they home in on something that makes them feel a bit Hipper-Than-Thou, and when it becomes popular they move on to something else they can be elitist and cliquey about. This is why Donegan moved on from "My Old Man A Dustman" to such art songs as "World Cup Willie" and "Beans in my Ears".