In response to the question of "What defines good rules" as far as the Song of Ice and Fire RPG...
(And I assume that the particulars of the setting are unimportant for the sake of the question, as while it is important to how things function, it's outside the scope of the basic question.)
In the game, the characters are assumed to be part of a noble house governing specific lands within the setting. Characters can be made to interact heavily with these rules (as in, they are concerned specifically with maintaining the reputation and fortunes of the house) or they can roughly ignore them, depending on the focus of the game. The Kingdom Building aspects of the game are as important or peripheral as individual tastes require.
The Houses are defined according to their individual Defense, Influence, Lands, Law, Population, Power and Wealth. The individual scores are generated according to where in the setting the Noble House is located, how long the House has been in existence, what sort of origin granted it nobility, and what sort of events have defined its history. (These are mostly generated randomly, although they can be picked with GM approval.) These scores are maintained through periodic rolls and PC interaction as necessary.
From these scores, certain qualities can be purchased, such as the specific castle features and land features. (Does the Noble House actually have a castle, or just a simple hall for feasts and gatherings? Where is it located? On a river for trade? Near some old ruins? How many smaller Houses depend on this one for defense, and what is the make-up of the militia? And so on...)
As the game progresses, the house fortunes may rise and fall, and depending on the direction of the game, they can upgrade certain features, which can take a period of time. As such, this can define how events impact it. Building a castle keep for defense can take as long as 17 years, where building a marketplace and attracting traders to your town might only take between a couple of weeks and six months.
And being that Song of Ice and Fire puts a great deal of emphasis on social interaction, I feel that it reinforces the "kingdom building" aspects of the game by requiring that interactions depend more on the characters' abilities as diplomats slightly more than how well they can swing a sword.
Which, considering the source material, only makes sense.