I am 44 and I started with GT3 at a friends house back in ... 2001? My niece got a PS2 and GT3 for Christmas (I think the same year) and I played that a couple of times. Then I played Project Gotham Racing at my friends house (he had all the gaming consoles, plus several full size arcade games). I remembered that GT3 seemed more realistic, so I would monopolize his TV (72" plasma) by playing GT3 on his PS2. Right after the release of GT4 I finally had a TV of my own and got a PS2 and GT4. I bought GT, GT2, and GT3 and occasionally played them. When GT5 Prologue was released I got a PS3. I won a copy of GT PSP so I bought a used PSP so I could play it. I pre-ordered GT5 and got it early on release day (store didn't open at midnight). The only other video games I play at home are the CoD series.
Gran Turismo is about 80% of my gaming experience and the reason I own a PS2, PS3, and PSP.
Without Gran Turismo and Speed TV, BBC America (for Top Gear) and Discovery/Science/Military/History channels, I probably wouldn't own a TV.