Personally, I don't think the quiz rankings mean much.
Many people tend to rate a quiz based on how well they did on it, not on whether or not it's a well-made quiz. Also, people tend to overrate quizzes on subjects they enjoy. In my opinion, if the rating system truly reflected how well a quiz conformed to good quizmaking standards (fresh and interesting questions, good grammar and spelling, plenty of interesting info) few of the quizzes now in the Top 50 would still be there.