I seek out interviews, books and essays by artists of various media in an attempt to understand their thinking about their work.
A very common thing among the very best is the foundational belief that what they are doing is selling emotion. They are making a thing that causes them to feel a certain way and then we look at, listen to, taste, feel, smell what they have made. The best artists help you to feel something too. The better the art, the more intense the feeling. Of course, what you feel is subjective and dependent on a host of variables. One person can feel revulsion and another feels revelation from the same work.
For me, the games I come back to are the games where I “feel” the most at the end of the session. Elation, excitement, fear on occasion- the best games and the best game masters are peddling emotion. Perhaps the first question a game designer or game master should ask herself, “What do I want them to feel?”