In order to understand bad content vs good content, we need to consider the context. An inbound marketing pro will tell you that relevance may be the most important piece but even relevance on its own is not enough. The context of course is related to audience, education, experience, culture, difficulty to create and as Seth Godin will say "how remarkable is it?". Thus, just as beauty, quality is based on the eyes of the beholder.
"Excellent job!" today does may not look so impressive six months down the road.