According to Louis Castle, "More than anything he [Steven Spielberg] gets people. I have made a lot of games, more than a hundred and I am quite accomplished in this field, even I don't have that kind of instinct."
It's a surprisingly simple characteristic that explains so much about his mastery of film-making, right? He gets people. And because he understands them so well, he's remarkable apt at tapping into universal themes, desires, and habits, and letting those insights guide his craft.
I can't help but think that's the core characteristic of a master game designer, too. They get people.
Think of Will Wright, when he's explaining how human beings learn through experimentation, and love learning. Think of Peter Molyneux, when he proposes that Fable 2 will touch gamers' hearts... not through romance, but through an unshakeable companion (a dog) and unconditional love.
If you need a demographic chart to know what people want, then you don't really "get people".