When you think about "quality" on Wikipedia, don't just think about any given article in isolation, but instead step back and look at the bigger picture: for instance, how every Wikipedia article about a movie has a similar structure, or how easy it is to hop from one species in Hymenoptera to the next. You also have to look at the things that aren't there to appreciate the degree of work that goes into making the project coherent.

Another instructive place to start reading about WP quality is the Featured Article process; in particular, try clicking into some of the discussions about individual FA candidates.

http://en.wikipedia.org/wiki/Wikipedia:Featured_articles