Look at 'Avatar:' the foreign ticket sales were over twice the domestic returns. The mind boggles at those kinds of numbers, but that's what you get when you effectively reach out to a global audience. If that kind of thing came to comics, it would undoubtedly change how people perceive the mainstream industry.
On one level, all of the characters in 'Game of Thrones' grow out of George R.R. Martin's imagination. Therefore they are his. As long as they are in the novels they are his. But the moment they step forth onto the TV screen, they become filtered through the showrunners. In a business sense, it's the same way with comics.
The first rule is you have to create a reality that makes the reader want to come back and see what happens next. The way I tried to do it, I'd create characters that the reader could instantly recognize, and hopefully bond with, and put them through situations that keep the reader on the edge of their seat.