What is Game of Thrones about?
Adam Rifkin stashed this in Game of Thrones!
Or, Game of Thrones is really NOT about the Starks at all.
It's about the Realm. Westeros itself is the protagonist.
The Starks play their part, but Game of Thrones is about so much more than the Starks.
Tyrion seems a lot more important to the story, frankly.
In fact, this is a good summary of the first three seasons:
three dragon heads!
A lot of major characters don't have POV chapters, including all of the kings for the duration of the war and after. The fact that a character lacks chapters from their point of view doesn't mean the story can't be about them. I would argue that A Clash of Kings is as much about Robb as A Game of Thrones was about Ned or A Storm of Swords was about Jaime. The difference is that we see Robb's story through Catelyn's eyes, rather than through his own.
But at the end of the day, there is no central, main character in ASOIAF. It's an ensemble of important characters. The story isn't about any one person (or group of people, for that matter). As /u/Digimonkeisari stated, the story is about Westeros. It just so happens that the first part of the story (aGoT and aCoK) is seen primarily through the eyes of the Starks.