Here is the list published by App Annie on their website for top apps on iOS Store in USA. Surprisingly Facebook is at number 13 in “Free” apps list. Not very long back, it topped the chart and stayed their for a good period of time.
Pokémon GO , the latest app sensation which has crossed 500 million downloads this week after its launch in July, tops the chart for grossing app (in App purchases).
Complete list can be seen on App Annie website at https://www.appannie.com/apps/ios/top/
You can follow App Annie on Twitter here.