I go through phases. Right now my current favorite is Barnacle Bay. I love its insular feel and the idea of a modern community on an island. It also seems to have a distinctly warm feel, like it was Mediterranean or Caribbean. It seems like the sort of place anyone can be anyone they want. I can imagine it being the setting of a fantasy novel where the setting is kind of halfway similar to our own world and half somewhere completely foreign. The only thing I don't like about is that its population is humongous.
I love Twinbrook for its very real feeling. It's the one I think most closely matches a real town.
I love Sunset Valley because it's so small and convenient, for the most part.
Riverview has my favorite lots. Bridgeport has my favorite starter houses.
Union Cove is like a circus wrapped in a picnic baked in cotton candy. Endless fun.
I kind of like how new worlds have turned into stuff packs for TS3. Sure, we pay for them, though there are also user-created worlds that are fantastic. I think the game is already incredibly complex, but new worlds make for great fun without having to add new levels to the game that may or may not really add much *coughcelebritycough*.