Good books, not great. Martin has built one of the finest worlds I've ever read but he's bogging it down with hydra characters (kill one, two more pop up in his/her place), kudzu plot lines, lack of progress, and 4,500 pages into the series, he still hasn't really introduced the wights/others, who were the center of the friggin' prologue in book one.
This series has all the makings of a big ol' mess in the sixth and seventh novels. If he continues down this path and then magically wraps up everything in the last 100 pages of the seventh book, I'm gonna be bent.
I fear that he has bitten off more than any writer could chew with this series. Stuff like having Arya wander around unnecessarily for, oh, about 2,000 pages show that he's just trying to juggle too many characters. He needed her character to not advance while other stuff happened.
And don't even get me started on character growth. Outside of Jaime Lannister, almost every character is the same in book five that they were in book one. Some have changed sides, some have done good, some have done bad, but they're all essentially the same people doing the same stupid things, only now some of them are dead because of it.