CHESS - play for the competition with the other
LEGO - play for the pride of achievement
MYST - play to find out the story closure
Games with story must appeal for closure, if not it will turn out a different concept of what is supposed to be a storytelling experience.
I believe that a lot of people are trying to build games with Lego concept behind, the game can have an overall goal but at the same time it will take player to invest in wild imagination to build new ideas.