26 and since GT1, but spasmodically, until about 1.5 years ago.
(Warning, boring long winded account of GT memories follows)
I can't remember when i got GT1, as it was a long time ago, but it would not have been very long after the release because I remember seeing a GT TV advert and being very impressed with graphics. And when I bought the game the opening movie, and the replays were immediately impressive.
Because i was young and didn't have that much money, and had just spent a fair bit of it on a game, i persevered with GT1 until i got good enough to play and eventually finish the game. I have early recollections of buying a car, winning bugger all $ for coming 5th/6th, spending that money on upping the power, which only resulted in me going deeper into the gravel when i failed to brake properly for the majority of the corners. (Then losing more money when trading that car in for a different car, which would respond equally badly to my early arcade style last second braking technique)
I know I bought GT2 prob not too long after it came out, and liked and played it a lot.
Because, I didn't get a PS2 when it came out, i didn't buy GT3 upon release, although i remember i tried it and didn't really like it, the handling seemed a lot more sterile, when compared to the two earlier releases.
I got GT4 when me and my brothers got together and all chipped in to buy a PS2 (i cant remember when but i think we only spent about $250(AUD) to buy it, so definitely later in the PS2 life cycle), but i didn't like the feel of GT4 either, it felt similarly dull and uninspiring like GT3.
When I moved out of home I took the PS1 with me so I could still play GT2, mainly doing arcade time trials v the ghost, and filling my garage with all the rare and manufacturer special cars.
Then in early 2009 i moved (temporarily) back in with my parents and i thought i might as well try GT4 again, I started where i'd left off last time, and being a bit more mature, I took the time required to get used to the more realistic (often understeery) handling (which improved a lot when i learned to turn off the default driving aids), but i still finished the game by b-specing the enduro's and over killing the shorter races. So when i moved back out from home again, I took GT4 with me, bought myself a second hand PS2 (as well as GT3 for $5) and started GT4 again from scratch, I also discovered the GTP forums, (esp the 200pt one) and have never looked back.
I'll no doubt get a PS3 and GT5 eventually, but I'm in no rush as there's still plenty I want to do in GT4 (re-do licenses, buy more cars, get more A-spec points, etc), I also want to see if can go back and gold the GT1 licenses, and I still haven't done anything in GT3 apart from the licenses either. (Not to mention now that I'm almost done with Uni I want to set up my G25 more permanently, which I know means endless time will be spent learning to drive all over again)
I also play GT Legends (60's / 70's era touring car PC game, i highly recommend it) online, because the place I'm currently living in has free internet, so i probably split my gaming time about 50/50 between GT4 & GTL at the moment.