Comparing a novel to a TV show is apples and oranges, but with Game of Thrones you can directly compare a fairly-faithful adaptation to an original screenplay. The writing on series 1-5 is conspicuously different to series 6-8, even though it’s mainly the same writers.
I wouldn’t even say GRRM is the better writer, but the process of writing a novel over many years and then rendering that into a 50-page script is just not going to give the same result as writing a script out of the blue. It’s like the difference between shooting on location compared to a soundstage, or using practical effects vs. CGI. If only subconsciously, you can always tell when you’re looking at a slice of a much larger world, with stuff going on outside the frame.
