I'm pretty straight forward: 1) Narnia because I like all the creatures that exist there. 2) Our world with muppets that are really alive.
Dangerous yes but even though the earth is dying it doesn't feel as grim as one would think. "There is evil on Earth, evil distilled by time … Earth is dying and in its twilight." The "few thousand strange souls" are "feverishly merry, for infinite night was close at hand, when the red sun should finally flicker and go black"So many of the fantasy worlds are so grim, I doubt I'd like to visit there. Even Narnia feels like a place more dangerous than interesting.
You beat me to both of them!Discworld and Lower London of Neverwhere. I like them not so much because I'd like to go there, but because very often I feel like I already am there.