Like many others I don't think PSP's sales and performance is anything to snuff at. The PSP did what nobody else could they managed to take a larger marketshare from Nintendo then anyone has ever taken before. Also PSP managed to beat GameCube and X-Box's numbers which is also very good for a handheld. The GameGear , Neo-Geo Pocket, WonderSwan , Gizmondo and the countless others that have failed over the years were all great systems but PSP out did all of them.
PSP revolutionalized the handheld market like no one has ever done before. They made a second console an actual legit choice. PSP also extended the PS2's lifespan by a few years through porting. The PSP also brought several new software titles to the market which many would not have seen the light if not for PSP.
I think if this new NGP manages to do half of what the PSP did it will still be more successful then GameGear which is the second most successful handheld console to date.
-JC7
"In God We Trust - In Games We Play " - Joel Reimer
