Tamriel
Thedas
Azeroth
Ivalice
Spira
Sanctuary
Post-apoc California and the Mojave
Koprulu Sector - oops forgot this thread is exclusive to RPGs
Various Pokemon Worlds - Kanto and Johto are probably my faves, though
The Underground or whatever the Undertale world is called

...running out of ideas, I'll get back to you