The two most important factors of a game are:
1. The Pull
2. The Push
These encompass what you are looking for and what you are dancing around (Growth, Relief, etc).
"The Pull" is something that entices the player to investigate something. A reward, a secret treasure to rack up a score, a secret game, a chance to catch a boob shot, whatever.
"The Push," coversly, is something that forces the player to move along. A damsel in distress, a treasure is stolen from the character, something that entices a strong negative emotion. (Think of when Aereth died in FF7, Sephiroth ran her through with a sword while as a player you could only watch in suspence. This pushes the player to desire some level of revenge against Sephiroth.)
Once the emotional aspect is attained, particularly in RPGs and Graphic Adventures, the rest is just academic.