For a product, sticking a "Greyhawk" label on new versions on those classic generic adventures just seems like pointlessly limiting your sales.
Better just to label it "5e D&D" unless the setting is in some way relevant to the adventure.
NB White Plume Mountain is in TftYP.
That's pretty much what they do, though they assume you are placing it in FR and include maps for FR, though every adventure anymore has a section on including it into an existing setting and where to put it, or even your very own homebrew setting and a relavent area of it to place the adventure.
What the question of the OP is: If you would play in Greyhawk, what adventures from the past would you play as an "adventure path". You do the conversions up to 5th edition, but use adventures from previous editions. There was nothing about how you would differentiate between Greyhawk and Faerun. Honestly, most of the names used within Greyhawk feel out of place in Faerun. Hommlet, Furyondy, Zagyg, Mordenkainen, most of the named wizards from the spells (Melf doesn't sound as high fantasy as Drizzt). If I had my old Greyhawk maps in front of me I could name a few more that haven't been said in this thread already.
As for my picks? I would start with Temple of Elemental Evil (I was honestly rather disappointed with PotA), and find a couple others that have Iuz and/or Tharizdun as part of it (Forgotten Temple of Tharizdun was mentioned earlier). Or, go with the Slavers series, or the White Plume Mountain/Barrier Peaks/the others in that series. Honestly, you could use the whole A series or G series, etc as an adventure path, with other modules or adventures from Dungeon tossed in. They may be light on storyline, so you'd have to fill that part out more, but it is doable.
Of course, I am a bit biased when it comes to the Elemental Evil adventures. I absolutely love the elementals, and it's my favorite part about Planescape.