Hi, I totally agree with what has been said. I think that what makes a good article has to do both on the content you write and with how you write it. 
 The section about someone's life, for example, seems to be well written if it shows how exactly the life of that person was relevant for the sake of the article (for example marking with more paragraphs the different parts of their lives), and does not consist in just writing a short summary of their life with very few details. In fact, I think that we have to keep in mind that the reason why we are contributing to Wikipedia is not only to make summaries of what we know, but most importantly to spread the knowledge of something, and to do so, we have to get into details.  
 Another thing that I noticed in the featured articles is that there is always a section dedicated to the scholars' theories about the topic of the articles (e.g. theories, impact, legacy, modern view) that help to put the subject in perspective.  
 Obviously, a good list of references and a good structure (images, paragraphs and such) definitely help!