Thanks for the reply. I've thought about this sort of thing a lot. I made a super-basic personal web app a few years ago for recording the movies I've watched and keeping a queue of movies I want to watch. I never added multiuser support or rating, but I gave ratings a lot of thought. My main problem is that a lot of words end up being tied together semantically: "good," "enjoyable," etc. really just end up meaning personal preference. I experimented with the whole gamut of ratings: from the most granular (rating camerawork, acting, humor, effects, etc.) to the least granular ("good" or "not good").

Should "quality" be affected by your film preferences, or is it meant to be an objective (and testable) hypothesis about what some group of people (critics, film bloggers, etc.) would report? If the latter, then I think the quality/rewatchability metric potentially misses information about "first viewing enjoyability," which is what I personally think is much more important than rewatchability.

In the end, I still have trouble with the "quality" metric. If it's meant to be objective, why use user input rather than some aggregation of real data (e.g. Metacritic or Rottentomatoes)? If "quality" is meant to be subjective, then it doesn't seem much different than "first viewing enjoyability," since "enjoyability" and "personal opinion of quality" seem by definition equivalent.