Looking at (http://www.appdata.com/leaderboard/app_store_apps?id=3781-top-free-apps http://www.appdata.com/leaderboard/app_store_apps?id=3781-to...), I'd say 10

Looking at (http://www.appdata.com/leaderboard/app_store_apps?id=3781-top-free-apps http://www.appdata.com/leaderboard/app_store_apps?id=3781-to...), I'd say 100 floors, Rope'n Fly, Sponge Bob.