Blackmoor 18
Dark Sun 8
Eberron 7
Greyhawk 12
Kingdoms of Kalamar 10
Lankhmar 16
Mystara 17
Spelljammer 13
The idea of any of these settings falling before some random 3pp nobody seems to really be into (I hear it's super geographically sound, or something? And the setting for the actually playable version of Hackmaster, I guess?) seems absurd to me. I may like the newer, genre-twistier settings on this list much better than Grognardia #1, #2, #3 and #4, but at least I can recognize those settings as forming the foundation of the game (and I've, you know, heard of them).
I'm calling Blackmoor as the eventual winner as it currently leads despite the fact that there is only one person who has given it any upvotes so far.