All Editions, All Universes...
Being as I first encountered and used the concept itself waaay back when as a direct result of the game, I'm partial to something along the lines of:
Dungeons & Dragons Multiverse (/Multiversal)
It not only encompasses all editions, but all alternate universes, allowing for multi-genre play as well, which Gary Gygax and at least Rob Kuntz and Jim Ward (off the top of my head) considered to all fall within the umbrella term of "fantasy" in its literal sense.
Cases in point:
- Gary's Greyhawk campaign when the party was whisked away to the Starship Warden (Metamorphosis Alpha), wherein Jim Ward took over as DM for such.
- Re: The work on Castle Greyhawk: I recall reading something relatively recently by Rob Kuntz (Pied Piper Press), wherein he referenced this very concept of what constitutes "fantasy," and in that piece also referred to his work on "The Machine Level" of said Castle Greyhawk.
- Expedition to the Barrier Peaks
- Conversion info fairly galore in the AD&D DMG regarding firearms, etc.