Both I and Mike Holmes have touched on this--I think that a thread on it might prove interesting:

Thesis: There are Three Personal Rewards of Gaming
All players who game and get an internal reward (as opposed to a social one, although functional play will include both) get one of three distinct categories of reward.

1. Thrill of Victory/Excitement of Challenge
2. Emotional Reaction/Engagement
3. Intellectual Stimulation


In a sense these would map to G/N/S and although this isn't accidental in my phrasing, they aren't really related (I can have an emotional reaction to a railroaded game).

Prioritization
It is possible for all of these to be equally prioritized: I can prize certain writers for how they engage me on an intellectual as well as emotional level--and there are writers who engage me on more of one than another (Dan Simmons hits both for me consistently, Dan Brown only on an Intellectual level and then only sometimes).

Excitement
The Excitement of Challenge category might best refer to simple excitement or tension. While this is almost always related to challenge, we feel excited in movies where there are tense situations we have no control over. I think this same effect can be seen in RPG's.

Reward
I've left out mechanical reward as a personal goal. Maybe it should be in there--it could be assumed under challenge (can I get a character up to 20th level?). It is my observation that people involved in character-building (as in Everquest) usually don't want too much challenge--they are interested in the aspect of creation and the construction of character (Intellectual stimulation through manipulation of system?)

There's a reason leveling up in many successful MMPORGS is called "the grind."

Usefulness
I think there are some very valuable uses to examining this.

1. Separating out player/GM power from it's goals (does giving players the option to make their own choices highten the emotional impact of a game in a general sense? Or only for some people?)

2. Identifying which techniques produce which results. Illusionism may be better at generating exictement than balanced fights, for example. If the GM can pull off the idea that the characters went through a narrow string of escapes that may distinguish between who wants the intellectual stimulation of a tactical battle.

3. Distinguishing social vs. internal rewards. It's my observation that functional immersive play doesn't rely as heavily on social feedback as more meta-game play. I'm not talking about taking this to a selfish level (to use contentious terminology) where there is no or vanishingly little social feedback--but I do mean a style of play where once in a while a player may do as he or she sees fit accepting the possibility of moderate disapproval or no feedback at all (the players are in separate rooms, the GM is neutral, and the player is pursuing a goal for internal reasons).

-Marco

Good stuff...

Over in Lee's thread , I proposed three goals for players to engage in conflict. I wanted to postulate some relationships between the two, but now, as examine the two categories, I see that any of my goals can map to any of your rewards. So perhaps I should ask a fourth question in my analysis:

What reward(s) are most important to the player?

But, all that aside, I think your onto something here...

Cheers
Jonathan