Yes, Farmville, but especially Farm Town. I like it better because it's more social. I can go work (and earn money) working other peoples' farms in real time, and have conversations with them in the chat feature.
You should have seen the Neopets community designed for children, but many older people were hooked. Cool concept....you have to raise a cute virtual pet (pokemon-like) and you have your pet play games, fight, and bid on the stockmarket (simulating the real one). It was a cool community. I got several students hooked. Though it pissed me off royally when my 10 or 11 yr old daughter at the time (this was years ago) got into a real argument with me and then in vengance killed off my Neopet yellow Kacheek . lol