No one can argue the importance of the Gran Turismo to Sony.  The long running racing series has become synonomous with PlayStation over the years, establishing itself as Sony's best selling property.

Polyphony Digital, the Japan-based studio behind Gran Turismo, has just released the latest sales numbers of the franchise.  The newest entry to the list is Gran Turismo PSP, released in October 2009.  According to Polyphony's numbers, the title has shifted over 1.8 million units.  Gran Turismo PSP was a launch title for the PSPgo, available both on disc and as a digital download.  Sony gave the game away to early adopters of the PSPgo for free.

These latest figures push the Gran Turismo series past the 55 million mark.  The highly anticipated Gran Turismo 5 is set to launch later in 2010, exclusively on the PS3.