Since you specified neighborhoods, my favourite overall would be the Puerto Llamante district in Selvadorada, followed by Myshuno Meadows (the large parks count as a neighborhood each, given they have their own NAP's and space), and the Crumbling Isle.
Puerto Llamante - Being from a similar place of origin, Puerto Llamante just beckons me to come home. If I could live there with my sims, I would, and the quaint, "mountainside village" feel is unmatched. I've gone as far as to remake the lots there into ones the people there can use, with one rental lot where visitors can take part in caring for the land and feel like they live there.
Myshuno Meadows - Having been raised in one, I have a love/hate relationship with cities. City Living brought the best of that type of locale, without the parts that make it improbable I'll ever go back. Myshuno Meadows is the essence of what I'd want in a livable neighborhood (one with more lots), with the little commercial area, patches of nature, waterside views, and communal areas. It reminds me of the best of where I once was, and it's a shame it's just a park by any other name.
Crumbling Isle - Whilst Sulani's miniature islands are the vacationer's idea of seclusion, the Crumbling Isle is the homesteader's. It's the closest one can get to having ones own private island, and unlike Sulani's, it has multiple lots to make of it whatever you wish. A community in seclusion, a tourist attraction, a private island, or even a mix of all three--the possibilities are tantalizing.