Grunker
We already had this discusion in regards to Witcher and Abercrombie, which i also consider par of the course as far as worldbuilding goes. We define world building differently.
As for world building i consider significantly better than GoT from the top of my head:
PoN by Bakker
Malazan by Erikson
Anything by China Mieville
LotR by Tolkien
Long Price Quartet by Daniel Abraham
BotLS by Wolfe
SotA by Tchaikovsky
see, this is my fucking issue
tolkien doesn't get a pass because he was first: i agree that his worldconstruction was thorough and good, but i don't agree that got's is any different
what martin lacks in mythological mysteries he makes up for with much more detailed and cool human cultures with LOADS more detailed aspects of behaviour and ritual than Tolkien have (and don't say silmarillon to me - you don't get to say that novels had good world-building because an encyclopedia exists that details it)... martin actually manages to differantiate human cultures from each other significantly without falling into the trap of "this is the greek culture, this is the roman etc"
even his fucking elves are p. cool (before he derps out with his lack of author-ability and the plot crumbles)
ffs, martin is a shit author; basically the sole reasons the first couple of books are saved is that his cultural construction and the insertion of characters into medieval institutions totally work - if got didn't have an unpredictable plot and an insanely interesting world, it would have nothing at all