My favorite in game world has to be either Bridgeport or Isla Paradiso(although the glitches are headache inducing lol). I love the cityscape and the apartment/condos. Isla Paradiso is beautiful for obvious reasons and I love the tropical feel for it, so many pretty pictures you can take.
As for store worlds I love Sunlit Tides and Dragon Valley. Sunlit Tides is my all time favorite world because I just find it absolutely gorgeous and it was the first tropical world I played in. I thought it was super gorgeous as well and I actually have a LetsPlay taking place in Sunlit Tides atm. Dragon Valley was really cool that old english style feel and the Dragons was a super cute touch! :3
As for my faveorite custon worlds I love love love Legacy Island lll and have another LP in that world, it has everything I need and the different sections in the world is really well incorporated. I also really love that they have places from the Sims2 neighborhoods as well as families from it.
Another favorite is Suva Duva Resort, it's literally the most beautiful custom world I've ever seen. It's so gorgeous and if you have the travelors mod you can use it as a vacation world, it's definitely worth the download! I would post pictures but I am stil a new member but if you want to check out the link you should!(http (nilxisdesigns.blogspot.ca/2013/08/suvadiva-resort.html)
Another CC world that I really like is Los Angelos by Casterboi, it's super cool and I find it has really cool niches in it! >> thesims3.com/assetDetail.html?assetId=7975351