Qualifications

Are certain audiences more qualified to judge certain works than others? Are other audiences not qualified to judge other works? Who decides who is qualified, and who is not? What does one need to do in order to become qualified? I think everyone has the right to judge a literary work, but I also think that some people may have more refined opinions than others. If two people looked at a painting by Pablo Picasso, and one of them had never seen one of his paintings before, and the other had studied Picasso's works for years, you would be more likely to listen to the second person's opinion. I would imagine it would be the same for literature. Some people would have more knowledge about certain works than most other people, and we would trust the opinions of the more knowledgeable people to guide our own opinions of the works. But how knowledgeable does someone need to be to actually be considered an "expert"? How much more training and research do they need to surpass everyone else? How does someone actually become qualified enough so that their opinion seems to matter more than the average Joe walking down the street? Any ideas?