In the past, since about 1987 or so, I've run my own homegrown campaign settings. Now that I'm older, lazier and busier, since about 2010, my D&D stuff took place in Greyhawk. I'm always looking to take some of the work load off of me. With 5e, it's a toss-up between Greyhawk (1st ed Box set) or Forgotten Realms (Grey Box). I typically don't add anything beyond those two because I run into people who know more about the settings than I do. By keeping it just those two things, I set a very nice and clear cut baseline for my campaigns.
Greyhawk is leading by a beak.