Nintendo's Four "I's"

In a keynote that Nintendo president, Satoru Iwata delivered to a packed house at this year’s Game Developers Conference, he spoke about the “Four I’s” that Nintendo uses as a standard for the games it develops.

“The reason, I believe, is that it meets the standards we set for all software we develop. We call these standards the Four Is.
First, is it truly innovative - something different from what has come before?
Second, is it intuitive? Do the control of the game and the direction of gameplay seem natural?
Third, is it inviting? Do you want to spend time in this world?
And finally, how does it measure up in terms of interface? Can the player connect in new ways?”

This is a great, short and sweet lens through which to view a game while you are developing it! There are, of course, many others, including Bartle's Four Player Types. But this one really hits the ball out of the park.