Worst to best for me including GT Sport.
7. GT Sport-
The best graphics, sound and physics of any GT to date do not save it from the main part of the game being still so flawed to this day. After nearly three years this racing simulator considers bump drafting on an oval bad, yet divebombing good, it simply is not fun to play way more commonly than any Gran Turismo should ever be.
6. GT6-
Quick Matches were the highlight of this game to me, but the servers were far to inconsistent to get anywhere close to the full enjoyment, and that goes for all other online modes as well. Having the largest car list and the ability to use community created tracks when the servers were still up made for quite unique single races, but the campaign mode felt virtually identical to GT5, the only change being a negative in no long endurance racing. GT6 was an excellent game when doing unique things, but between the iffy online servers and rehashed offline campaign, fun replayability is fairly rare, especially now with no servers.
5. GT1-
Probably about as good of a starting point as possible for the series given the era it was released, but the graphics, physics, and small amount of cars and tracks don't hold up very well. I don't think that these factors make for an overall negative experience though as long as what is there is fun, and it is. There is nothing to me that is completely boring and or annoying plus there is still fun to be had even now with so many successors.
4. GT2-
GT1 but with a bit better graphics and physics (though still outdated). The car and track list is great plus I really like the layout of the menus.
3. GT3-
I understand why this was the best selling GT of all time and is still arguably the best ever. For the time it had unreal graphics and was seen as the closest thing to real life there was. So much so in fact, the day GT3 released in the US my dad traded an old, rusted station wagon to his friend for a new PS2, memory card, controller, and GT3. The station wagon lasted about two weeks before it was too expensive to be worth fixing while the PS2 lasted about six years and GT3 still works today. Given that soon after I started playing GT3 as my introduction to the series, I guess that was a good trade.
Though all things considered I think GT3 has the biggest case of nostalgic bias of the series. People flocked to this game in particular for the next gen graphics and physics, neither are exactly what would be considered so now. To me cars, tracks, and features are the most timeless parts of a racing game. I don't care much about graphics and as long as the driving physics are fun, I am happy. While the game itself offers mostly flawless fun, what is offered in total is not enough to warrant GT3 being the best to me because of the smaller amount of cars, tracks, and features, though it is still a great and legendary game.
2. GT5-
GT5 had everything, a massive amount of cars and tracks, physics that still hold in my opinion, a unique and lengthy campaign mode, Bspec characters that could progress through campaign mode, HD graphics that still make the premium cars look decent, fun and varied optional challenge, a course creator that still works, a large player base to message and trade cars with, and online servers that could actually handle all of this. Also Jenkins. Granted, everything it had was not executed the best, though to me nothing was executed overall poorly despite what many people say (when I can I may do an in depth video on that). GT5 is one of the greatest racing games of all time to me.
1. GT4-
GT4 has most things, and what it does have was implemented in a nearly perfect manner. The best original music of any game paired with so many icons cars, tracks and events makes for the greatest racing game of all time. Overall it is the community that makes GT Sport worth playing whatsoever, GT6 having the occasional unforgettable moment, and GT5 having nearly countless worthwhile moments, but that doesn't make the games themselves better, because playing with the community is sadly temporary. When solely competing against yourself and the AI never gets old, that is unmatched.
As a somewhat awkward, lower wealth class kid that grew up in a small town, I didn't interact much with others in the real world and I didn't have good enough internet at the time to interact virtually as well. That traded in PS2 was one of my main forms of entertainment and GT4 was the number one game I played. From what I remember, I enjoyed every minute of it and had no regrets.
As a somewhat awkward, lower wealth class adult that is still in that small town, I don't interact much with others in the real world now also because of coronavirus. My internet is now below average which is usable so I do interact virtually some, but due to the only Gran Turismo still with online being the worst one, I seem to be socially distancing virtually now too. So ultimately I went full circle and started to enjoy every minute of GT4 (that isn't license tests) again. Now I don't have to remember the past good times and while playing I can briefly forget the current bad times.
I still most certainly have no regrets.