Babylonians are the best because you can reach Europe, Asia and Africa easily from your starting position, and the turn you capture a city you can start cranking out units! This means you can go around capturing cities, using them to build military and as long as you leave them empty you can recapture them the turn they go independent or when you collapse. In my American Dream game I was prepared to deal with multiple collapses but amazingly I didn't suffer one. I find that a combination of courthouses in every city and early forbidden palace, summer palace and strong economy will counterbalance even the wildest expansion... BTW sorry for the late reply