The Sims Social, the new crazy fad taking over on facebook that litters your newsfeed with "YOUR FRIEND HAS SENT YOU A THE SIMS SOCIAL REQUEST" has taken over Zynga's Farmville for daily active users. The player retention for the game is pretty good as well, with the average user spending 15-20 minutes per session online.
The Sims Social sees 9.3 Million users per day, while Farmville still sees a surprising 8.1 Million. Right now, the top dog is Zynga's Cityville, with 13.9 Million users.
All of those are dumb fucking mirco-transaction shit games.