Ourworld is pretty awesome, but if you are specifically looking for 3D avatars then I suggest you check out Meez. I play it a lot and so do most of my friends and it's pretty cool.
Also if you like that you will also like games like The Sims I think. You can control a lot about their life and how they look, and hey even have kids and things like that, so yeah, sorry if that didn;t helpLots. I'll give you some friendly ones.
-BinWeevils
-ClubPenguin
-AnimalJam
-Meez
-Woozworld
-Ourworld
And there are lots more but I don't want to list 100 sorry.