The best Series? Hmm tough joice. There are some really good ones.

Steven Erikson's Malazan Book of the Fallen is superb.
R. Scott Bakker's Prince of Nothing comes very close to the MBotF.
I really dig the world and characters in Michelle West's Sun Sword sixtet.

Martin is not bad either. He is a bit slow in writting the damn thing and his world is quite standard-ish fare. But his characters are very well written (i think nobody writes as good a dialogue as he does).

@ LS - Jebus : with your list of criteria why you like ASoIaF you should totally try out Erikson and/or Bakker. They both totally kick Martin's ass when it comes to complex cultures and history. Shades of grey is also very much how i would describe both stories. Give it a try.