Its difficult to overstate how influential the original Gran Turismo was upon its global release in 1998. Sony was aware of this, as you can tell from that grandiose marketing claim you see above, from a print ad in the run-up to the games release that, yeah actually turned out to be entirely valid.
Recently Digital Foundrys John Linneman explored the series past with a two-part retrospective focused on the franchises PlayStation and PlayStation 2 entries. It explains, from studio Polyphony Digitals inception to the games release and beyond, how the team was dedicated to pushing the capabilities of the original PlayStation, hardware that would be considered extremely rudimentary by todays standards. They succeeded, realising a quality of driving simulation that wasnt thought possible in the late 90s.