I hope James is right. I've never been involved with the RPGA or known anyone who was, so to my perspective it seemed as though Greyhawk received token support for the first couple of years in 3.0 supplements and Dragon/Dungeon, then *poof.* There was no effort whatsoever to market the setting to non-RPGA members. The D&D Gazetteer was just a tease, whereas the Living Greyhawk Gazetteer was the essential setting book but had nothing approaching the production values of the other core setting books and wasn't aimed at the general market. In general, there just wasn't much support for those of us not interested in the living campaign, who just wanted it to be supported like any other setting.

FR got a pretty, color hardback and its own line of supplements. Then Eberron came out with a stunning, full-color hardback followed by hardcover(?) supplements. Granted, everything 3.5 seems to be full-color hardcover (which is nice) but one can't fail to see original "default setting" as the read-headed stepchild by comparison. And how long before they start using names and locations from Eberron as examples in the core supplements (if they haven't started to do so already)?

I'm not saying that Eberron necessarily will become the default D&D setting, but I understand that WotC intends for it to be just that.

If I'm not mistaken, there's about to be a Greyhawk book put out. I don't remember what it is, I'm sure AM could tell us.  I do know that there's a kick going around one of the living grewhawk yahoo groups in which I lurk (I don't remember if it's the LG or Verbobonc one) that we should all buy the book/pdf to show how much support there is for publishing Greyhawk books in the future.

But I see what you're saying with FR and Eberron having all those books, makes Grewhawk seem the red-headed step child.

Expedition to Castle Greyhawk will be the upcoming mega-adventure released by WotC later this Summer.  It'll be along the same veins of the Ravenloft and Demonweb Pits (the latter is basically a return to Planescape) that are already on the shelves -- a hardback book that's a mixture of setting and adventure.  I don't have either one, but I've read online that they're pretty good.  There's been rumblings from some of the WotC regulars and freelancers that depending on how well Greyhawk sells, among other unnamed factors, we'll see more GH releases in the future.

Personally, I'm holding out hope for an Expidition to Mystara, Known World and/or Hollow World, but I don't think it'll happen.

Planescape, especially when combined with Spelljammer.  I'll caveat here, however, that I think Eberron is the best 3.x campaign.

Greyhawk is pretty neat. Planescape is exciting, and Dark Sun looks good. I have the 2ed AD&D Lankhmar core rules, and those were great. Is Conan 1e (AD&D) a setting? Conan had a couple adventure modules, with descriptions and maps of the Hyborian world, plus stats for Conan and company.

Wow, 6 pages and no love for the Iron Kingdoms?

While I don't like D20 for the rules, the setting is a rich tapestry.

Voted for FR - I started with AD&D, so FR IS DF&D for me.  I've read a lot of Greyhawk stuff - it was just never as evokative for me.  FR is just balls out awesome.  Even when I hated the AD&D rules, I still loved the FR setting - even before I read any of the novels.

VERY close second is Birthright.  Fucking AWESOME setting that changes things up and makes the game more distinct, without tossing the baby out with the bathwater.  Loves it.  Wish WOTC would do a 3.5 Birthright book.  It would fit VERY well with 3.5 rules.

I voted "other"  because by me two of the greatest D&D settings ever were not included.
Midnight.
Thieves World.

Both are fantastic and well rounded. And I'll throw The Black Company into in, too.

For me it's the Wilderlands by a stretch.
Followed by Mystara and original Greyhawk