Drama - It tells a emotional story (without any romance in it) that appeals and starts giving you questions. (Ex. One Flew Over the Cuckoo's Nest) And also it covers a large section of different sub-genres.
This was a very hard question because a movie isn't good because of it's genre.
For example Stanley Kubrick (A MOVIE GOD) has never done two movies with the same genre (with the exception of War, Full Metal Jacket and Paths of Glory).
And almost all of his movies are today masterpieces for its genre.
And Mystery is also a very good genre, take The Sixth Sense for exampel.
It keeps you thinking all time and sometimes even gives you creeps.