I have to say that there are not much neighborhoods that could satisfy my Sims experiences especially after all the expansions added into the games. Some worlds are beautiful but its not build for all exp, there are bigger worlds with many lots and rabbit-holes provided but its not as beautiful, I guess that why many people prefers to create their own neighborhood for the games.
I myself have created a world to fit in all the exp that I have, it still in the process and still stuck in the terrain sculpting and painting, which is very irritating and seems complicated to create just a simple big world to fit all those rabbit-holes and community lots. So basically I started out with some inspirations from SimsRealty's Elba Village, this is one of my favorite neighborhood as one of the reason is that it includes downtown and uptown area. I'll be posting some of the pictures later when its almost done, I guess I'm still quite a long way from finishing it and play with it, as I found glitches with the road, and I'll be doing more testing with it.
Anyways, besides Elba Village, these are some of my favorite town that I love to play with before;
Sunset Valley
The first town I've played and still comfortable playing with it and perhaps less glitchy and safer to play with, it somehow feels more at home and I've known most of the characters in this town, however there are not much spaces available to includes the exp community lots.
As what I read from a post in The Sims 3 Forum, EA did combine Sunset Valley and Riverview, but they separated it before the launching of the game. I'm not sure why, but definitely not for sale though, as Riverview comes as free store item as you registered your game.
Twinbrook
This town is beautiful although its foggy and not sunny as Sunset Valley, it still worth to play with it. However, I found a glitch or bug, [not sure which one, but definitely a problem] when I wanted to move my Sims to another house by edit town mode, I can't seem to click on houses after that. I guess they have overcome this glitch with the new patch, as I'm no longer installed the ambition pack.
Bridgeport
Sunlit Tides - Gold
Storybrook County
Lunar Lakes
Palm Grove
Strange Valley
Aurora Skies
Hidden Spring
Moonlight Falls