OK, I haven't seen the series.

I actually wouldn't doubt its overrated-ness. I remember people going nuts about 24 and Lost. I watched 24 and it was laughably bad (but the concept was great. Lost went nowhere — but generally looked good.... until the later seasons. I think that GOT may end up the same. The big budget and scope set it apart... but overall it may suffer (especially from what I've heard of the final seasons on CB and other online sources).