It takes place in a fantasy world, not medieval Europe.

This is a question I see here from time to time, and it's one I struggle to answer well, because the simple and correct answer is that the question does not make sense. GRRM insists on being "inspired" by medieval events, but it would be more accurate to say that he's inspired by a secular/protestant modern lens on medieval events, of which he seems to be entirely unaware, particularly evident in the parts of the story currently on television. It's like trying to use The Lion King to reconstruct the legend of Amleth (Shakespeare's ultimate source for Hamlet).

And at the same time, it's important to recognize the work this claim to historical inspiration does: it provides a substantial degree of authority to the text, and allows the author (and show creators) to get away with a whole host of things which would not usually be socially acceptable in the name of "realism."

So I guess the question boils down to whether or not GoT gives a proper sense for the "feel" of the medieval past. And here, too, the answer is no. It plays up the barbarity, ignores ordinary life, and renders a body count which is quite clearly unsustainable for any species, never mind a civilization. It constructs a particularly one-dimensional view of the Church drawn almost entirely from protestant polemic. Also, dragons.