I'm sorry for you but PSVita has not only hardcore game nut also casual game like little deviants,sound shape,little big planet.
So what you saying is false PSVita is like 3ds a hardcore/casual handheld consoles.
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