The franchise debuted in 1997 on the original PlayStation, and made the shift to PlayStation 2 with Gran Turismo 3: A-Spec in 2001. The series' first PlayStation 3 retail release recently arrived in the form of Gran Turismo 5 Prologue, which is meant as a sample of the eventual Gran Turismo 5.
While North America has only received five Gran Turismo games so far, Japan and Europe have seen seven due to Gran Turismo Concept 2001 Tokyo (PS2) in 2002 and Gran Turismo 4 Prologue (PS2) in 2003.
Sony noted that of the 50 million units shipped, 2 million of those were Gran Turismo 5 Prologue. However, it was not clear if Prologue's contribution only referred to physical copies, or if it included digital downloads of the title through the online PlayStation Store.