I've been running Greyhawk since 5E came out. I'm currently running Saltmarsh, and have a general campaign outline that will end with the Final Enemy. Prior to that I ran a Furyond/Veluna/Keoland campaign based on classic 1E Greyhawk adventures. Afterwards I ran a Nyrond campaign, but that one didn't pan out the way I wanted. After Saltmarsh (and a hiatus), I've got three different campaign ideas already in mind (not to mention a fourth my players showed interest in during the Nyrond campaign).
Nice thing about Greyhawk is that there's a lot of information from prior editions, and most of the mechanics are fairly irrelevant. Purists like myself might limit options available to fit the setting, but others can "kitchen sink" the setting. Really the only aspect the setting really lacks is an oriental region, which was supposed to be Kara-Tur in the west, before it was absconded by the Realms.