These are the sales data taken from Capcom's website:
PSP MH:
Monster Hunter Freedom : 1.3M (2005)
Monster Hunter Freedom 2 : 2.4M (2007)
Monster Hunter Freedom Unite : 3.3M (2008)
Monster Hunter Freedom 3 : 4.7M (2010)
Wii + 3DS
Monster Hunter Tri : 1.9M (Wii) (2009)
Monster Hunter 3 (Tri) G : 1.9M (3DS) (2011)