Skyloft would be wonderful, especially if it was right after they discovered the Surface. I would love to fly on the back of a Loftwing, soar above the cloud cover each day, and explore the strange, exciting new land below.
The world of Star Fox would also be pretty cool. Wind Waker would be nice, though not as nice as Skyloft, and Ocarina of Time (if only for the idyllic childhood vision I see it as), and hmm most Zeldas now I think on it. Especially if you were part of the Cycle and was reborn into each new game and got to experience all the wonder (and, yeah, terror) of each era (with lololol some HW fun in the afterlife staging area).
Honestly, Nintendo's worlds are just so full of wonder and fun that any of them would be an enjoyable experience, especially if you were a Hoid-like being who could just step into and between each one. Spend a few weeks on the Great Sea, pop over to Skyland for a nice few days, then frolic in Dreamland until you get bored and wander over to Corneria. Sounds good to me!