I can't decide between three; Jubilife, Pastoria, and Hearthome.
I never understood why I liked Jubilife, but it just seems pretty cool to me. For some reason it reminds me of New York city. . . just don't ask why. :P
Pastoria, in my opinion, just as beautiful scenery. I've always liked the Safari Zone, too.
Hearthome is great, because of the Contest Hall, Poffin House, and Amity Square.
So, it's a tie between those three. But if I HAD to pick, it would be Hearthome. There's just so much to do there.