See, the thing is, I don't think there has really been an honest attempt to sell GH material since 1e. The 2e stuff was a combination of a middle finger to Gygax (Castle Greyhawk megamodule, ugh) and a bunch of okay stuff that tried to make sweeping changes in the world (Greyhawk Wars, From the Ashes, et. al.).
You're missing an era of Greyhawk releases there.
The first era of Greyhawk releases is 1978-1985 (or thereabouts) when Gygax was at TSR. This is when the world is developed primarily through adventures. Giant/Drow, Slavers, Hommlet, White Plume Mountain, Tomb of Horrors. While this rather defines Greyhawk, a lot of this is accidental. There's not really a big plan here. The idea of the adventures actually changing the world hasn't arrived yet. Yes, a lot of them *could*, but the idea of the world changing at TSR instead of just in gamer's homes isn't evident. Not only that, but a lot of the adventures aren't really Greyhawk adventures at all. They're just placed there because it's TSR's house setting.
Following 1985, the only releases for the next couple of years are the supermodule compilations. These are sort of significant in linking the adventures more to Greyhawk, but they do have their own problems.
From 1988-1990, we hit the real problematic age of Greyhawk releases. You've got a faction in TSR who want to treat the setting well, and you've got a faction who want to destroy it. From the first faction, you get the Greyhawk Adventures hardcover, Greyhawk Ruins, and the WGA adventures. From the second faction you get Castle Greyhawk, Puppets, Gargoyle and Vale of the Mage. In, in the middle, you have the City of Greyhawk boxed set, which I'm probably being unfair to. The boxed set really is part of the same strand of releases that leads to the Greyhawk Wars (the WGA adventures), but I have some problems with how its put together, most notably with its naming schemes. However, it could also be the best city release for D&D until Neverwinter came along a couple of years ago. (Sharn might be in there, but I've major, major problems with the various Waterdeep releases).
Ignoring the joke modules from RPGA and anything written by Jean Rabe, this era is the first serious attempt to properly present Greyhawk as a living world. It's not helped by the serious adventures not being very good (this is true of almost every adventure post 1985), but for the first time you get the impression that the designers are attempting something here. It also represents a massive shift from the first era of Greyhawk products. When we look back at the glory days of Greyhawk, we think of that first era. There's just one problem: It's an unsustainable era. The original Greyhawk releases assume Greyhawk is in stasis. Wizards would later do this to Eberron. And while showing just a snapshot of a world works, and works really well, at some point you've detailed everything. The timeline has to move, and the original Greyhawk releases aren't connected enough to the world to allow that.
To their credit, the TSR designers realised that, and they gave the world to Carl Sargent to get moving. And he did. By blowing it up.
I have massive problems with the Greyhawk Wars (beginning with their name, which makes no sense in-world) and From the Ashes, but the one thing they did absolutely right was change Greyhawk from a setting you could place adventures in into a setting that inspired adventures. This isn't to say that there wasn't some inspiration in the original Greyhawk sets, but From the Ashes makes the setting into something that appears much more dynamic.
And so from 1991-93 you have an era where TSR explores this new world, producing a number of sourcebooks for the setting (and very few adventures).
And then Greyhawk dies. Ivid the Undying is (ironically) cancelled and only released as an electronic document a couple of years later. The shake up of the world has failed. It's actually hard to tell from the outside whether this is more due to internal politics or bad sales, but I do know there were a lot of people unhappy with the From the Ashes world. It's changed the feel of Greyhawk too much. From telling stories of adventure, we've moved to telling stories of struggling to survive in the new world order. (This isn't entirely accurate, but anyway...)
It's 1998 when Greyhawk is next visited. Roger E Moore is in charge of Greyhawk now, and Wizards own TSR. From 1998-2000, we have Wizards attempting to fix Greyhawk. The year is advanced to 591 CY, and a bunch of clean-up work is done to make the feel of the world much more like that of the original boxed set, whilst retaining the idea that the setting generates adventures. Unfortunately, the actual adventures published are lacklustre. Return to the Tomb of Horrors isn't that bad, but the Star Cairns series are extremely forgettable. And after about 12 products, we're done. The culmination of this era is the
Living Greyhawk Gazetteer, which is one of the true gems of Greyhawk products.
After that, it's the 3E era, and although the first eight 3E adventures are, in theory, set in Greyhawk, they aren't really, and there's a lot of Living Greyhawk material which is mostly invisible to the larger D&D population. And there's Return to the Temple of Elemental Evil, which has its own, major problems.
Throughout all of this, you have Dungeon magazine occasionally producing content for Greyhawk. Most of it is forgettable. A lot of it I've never seen. (Most of my experience of Dungeon magazine happened in the 3E era). About the only significant release is the Age of Worms AP. (Neither Shackled City nor Savage Tide really play into the core Greyhawk world - they're too far off the edge of the map). But Dungeon magazine should be noted.
So, the eras of Greyhawk publishing - to me at least - feel like 1978-85, 1988-90, 1991-93 and finally 1998-2000.
All of which feed into why it's really, really hard to bring back Greyhawk.
Cheers!