I haven't been playing too long, and my taste is fairly basic. :p Haven't looked at Custom Worlds yet. Appaloosa Plains, Moonlight falls and Twinbrook are some of my favs so far. Appaloosa Plains is great because of the already existing pet areas!! I often play with pets and it's always nice seeing them have a blast here.
Right now I really like Twinbrook, it's always raining and so misty it makes me feel at peace with nature. It's super simple as a town, and I love the random railway tracks littered around my sim's house. It has a lot of character. :) Makes me feel secluded.
Personally, I'm waiting for a sale to get Late Nights and start looking for city builds? i want to see how people design urban builds. :D