Having played all three GRID games, I can basically make my own assessment on which I like best.
* I totally feel GRID has the best Career, since you feel part of a race team and that you really feel like your efforts are going towards being a motorsports legend. GRID Autosport has a realistic racing feel to it, but it really is diluted since you don't get the freedom like with the first GRID in making your own team. GRID 2 seemed more predicated on establishing a rogue racing league and growing its popularity rather than trying to be a racing superstar. In addition, the addition of hiring teammates and shopping for the best talent makes you feel like a proper racing team instead of always having to be the breadwinner. It's one of few games where you feel like you have an actual TEAM rather than just trying to be an individual legend.
* I think GRID set the tone for what the evolution of the ToCA Race Driver series is with its gritty racing. GRID 2 was a little less gritty while still being intensely difficult, and GRID Autosport is more professional than aggressive.
* GRID Autosport is by far the most beautiful graphics-wise. However in terms of menus and UI, GRID is surely the most expressive with the 3D menus and screens. GRID 2 is the most stylish.
* GRID 2 has about my favorite of spotter radio. The guy doesn't scream in your ear or anything. He can be a bit annoying in trying to offer you stuff, though. Almost as if I have to be like, "okay. Let me access [this feature] so I can get him off my backside..." Even still, I have to hear it from him about the Timeline feature (for example). GRID Autosport's spotter is probably my second favorite. Which... makes the GRID spotter my least favorite. I do like in all three games that I can be called by name or by nickname. So it's always good every now and then to hear "John" in being discussed certain things. I don't feel random.
* All three games have excellent musical scores, especially in the menus. It is tough to be tired of hearing each of the songs.
* Driving in GRID is probably my favorite of the three in terms of physics. I say that because I think the first GRID defines the style of GRID games best- it is a simulation-style racer with a little arcade mixed in to please both audiences rather than be exclusive to one specific style of driving. GRID actually makes this intense style of racing and driving fun. Normally, I wouldn't be all into arcade-style racing like with modern arcade racers, but GRID actually makes it fun. Only regrets for me would be that I wish I were better at drifting and at togue.
So I guess what I am saying in this post is that I fancy GRID more than GRID 2 and GRID Autosport as a whole. I love all three experiences, but there is just something about GRID that makes it the best of the three GRID titles. It's much the same way I think Gran Turismo 1 is the best of all GTs because of the whole experience and that bit extra. It goes to show that sometimes, the best in a series is the original and that not every sequel is not always better than the original or a previous title. That's why if you polled some people like on YouTube or something, a number of people would probably say GRID 1 is the best. There were people who even thought GRID 2 was a disappointment compared to the first one. One video was even talking about how GRID Autosport would "fix" GRID 2's woes.
Needless to say, I seem to enjoy GRID 1 more than the other two. Nothing new to report from my GRID experience except that I hired my first Pro-level teammate and that I recently bought a Corvette C5R for Le Mans and for some of the races that require the Corvette racing cars.