People say psvita should have system unique new IP to succeed but it's seem it's not true ,bestsellers games in PSP are spin off not new unique IP it's the same thing for vita.
PS4 - over 100 millions let's say 120m
Xbox One - 70m
Wii U - 25m
Vita - 15m if it will not get Final Fantasy Kingdoms Heart and Monster Hunter 20m otherwise
3DS - 80m







