Individual sites have diffrent rating systems; each having its own advantages. For example, IMDB provides user ratings. The presence of a super-star, or high advertisment budgets may skew these. Rotten tomatoes, on the other hand provides critic ratings. Award nominated movies and good technical work may influence these. A good picture will have a high Tomatometer as well as IMDB rating.
This tool provides the user a way to easily compare diffrent ratings for a movie.
Currently ratings from IMDB, RottenTomatoes, MetaCritic and MovieWeb.com are supported.
Cinemeter is now avaliable for Android: http://www.appbrain.com/app/cinemeter/com.kiran.android