iam not using facebook and iam not interested of any social network and if i wana play games i play big games with big graphics like :
elder scrolls v skyrim
batman arkham asylum
..tons of games
and if i wana learn something i read from books, Wikipedia, toms hardware
I actually can see it being "successful" if games can be bought and gifted and are played with your friends on it. But this success will be limited to a small number of games much like any other app store, most apps are buried and never get any attention. Still can be quite profitable for Facebook still but the actual developers will mostly be in disappointment.