Read "One Quack Mind: Good Duck Artist Carl Barks' Best Work Sadly Lost to The Dustbin," by Christopher Skokna, and then go see the exhibit and make up your own mind.
UPDATE: Andy H of GEM wrote in to note, "The two Carl Barks non-Disney series we have representations from are:
Famous Figures of History as They Might Have Looked Had Their Genes Gotten Mixed with Waterfowl
Kings and Queens of Myth and Legend."
While I agree with the Baltimore City Paper review that these aren't great works of art for all time, I do think for the student of comics or Carl Barks, they're very interesting and rarely seen. So there.