My brutally honest thoughts:
Loved the early Gran Turismo games. GT2 was my favourite racing game for a long time. It's aged terribly though; I went back and played GT2 a few years ago and I was amazed at how ugly it looks now.
The last GT I played was GT Sport and it was decent, but felt very lazy. I can't believe the AI cars behave in exactly the same way as they used to 20 years ago - still trundling along in these obnoxious, identical, well-behaved convoys. Embarrassingly bad, just like the damage modelling and physics. I wish fans demanded better tbh, rather than defending that kind of lazy crap. At least some of them pushed back on the single player aspect being completely gutted, and that forced a response and partial remedy.
GRID was by far my favourite racing game of the PS360 era. Time also hasn't been kind to it, and the last few GRID games have been really lacklustre, mostly because they took away from what made the first game so great (the excitement, spontaneity, and immense variation in races caused by the damage physics). I haven't played the most recent one, although the PR for it was focused on forcing a narrative into the series so I can't say I have high hopes.
I also liked the DiRT series, but again recent entries have kind of sucked - far too shallow, almost all of the tracks are tiny, and there's not nearly enough content, so it gets repetitive real quick. Codies has gone from being by far my favourite racing dev to all style no substance in the space of a few years.
The MotorStorm franchise was also great from that era - especially the first two games. The final game was a real dud, but it's been a while - I'd love them to reboot this series.
Moving on to the current era - one of the best racers from the last few years was Wreckfest. It has the kind of updated damage physics and modelling that made me fall in love with the first GRID. Needed a little more of everything tho - tracks, events, race types, etc. It's also way too rubber-bandy when playing against the AI. Fuck rubber-banding - keep that rubbish in kart racers.
And finally there's WipEout (rip Studio Liverpool), which was consistently excellent across all of the gens, from WipEout 2097 back in 1996 all the way up to Omega Collection in 2017.
I really must play a Forza Horizon game at some point, now the series is on Steam. They all gets great reviews and people seem to love them... but then again recent Codies games have also got great reviews and they're pretty much just flashy trash. A few pretty special effects and the critics lap it up, like a fucking Marvel movie.