Did you miss the part in the OP where I said FR wins the IRL award?
GH cops less flak online than FR for a variety of reasons. I am speculating on what those reasons are.
I cannot comment on how much love goes one way or another, but I think you are spot on with your assessments. Having more of a blank slate to make your own is attractive. Many modules could take place there, but unless they are used in your campaign they may or may not be relevant. Your Greyhawk can be very different than mine.
The same thing can be said of the FR but look at the veritable mountains of material created for it--several editions worth. Books, games and so forth. There is a glut.
I do not think we should discount flavor either. There is some cool stuff in FR, but the dark and brooding greyhawk is different in its fantasy generic-ness.
I think FR seems too convenient. There are too many super heroes. Getting lost in Greyhawk seems more desperate and remote in a sense...there are fewer Elminster/Drizzt characters ready to hop in and help.
Conversely, we are using Sword Coast AG and the maps to flesh out SKT. None of us are well versed in Realms Lore and none of us care about it. In this way, the Realms can be fine with crabby players like me. I am capable of ignoring the cartoonish crap...
Second aside: when the forgotten realms boxed set came out in the 90s, we thought it was pretty cool. It changed over time. And that is another reason I think overexposure is part of the problem and with it "overpopulation" with heroes. Back then we actually saw the Realms as more remote and LESS populated! That seems kind of funny decades later...
