Favourite racing game is always highly dependent on what I am looking for.
Forza Motorsport 4 (Not Horizon) was one of the best racing simcades i've enjoyed playing, it has solid sim-ish racing and it is very satisfying to build up a garage and take a car for a spin on some of the gorgeous original or real life racetracks. Unfortunately, it's an xbox 360 exclusive and not backwards compatible on xbox one or series x, so not really playable on current systems. I am stll looking for a similar experience on a modern pc.
I also enjoy "Project Cars" and it's sequel "Project Cars 2". I can easily play the games on my current PC or the Steam Deck, but the game can be challenging on a gamepad - not impossible, but managable. It does lack some beautiful original tracks as it only features real life circuits and it does lack the satisfaction of having to "earn" and build up a collection of cars and making them your own. Unfortunately, both games have been delisted on storefronts and can no longer officially be purchased, but if you can get your hands on a PC Key, you can still enjoy the games on a modern system.
If I want to enjoy some sim racing, I'll go with Assetto Corsa or Assetto Corsa Competizione. Great fun with a steering wheel, not really my thing with a gamepad. Modding possibilities for AC are basically endless on PC, but again, lacking some sort of progression system that will allow you to build up a car collection.
Forza Horizon 3 with its Hot-Wheels Expansion was probably my favourite open-world arcade racer, unfortunately it's also delisted, and while I still have the physical xbox one version, that means I can't play it on PC. Forza Horizon 4 (with the Lego expansion) is the next best thing (still far better than FH5) and is still available on PC, but will also be delisted in december (grab FH4 while you still can!)
I have also spent a lot of time playing Burnout Paradise, but I still prefer Burnout Revenge over it's younger open-world brother.
Wreckfest is a great spiritual succesor to the already great Flatout 1/2 and certainly the best banger racer you can currently get. The damage model is very convicing and it's good fun to wreck some CPU racers.
BLUR - an underrated battle racer, with a really fun 4 player splitscreen. Calling it "Mario Kart with real cars" is, imho a bit too simple, but it does get the point across quite well.
Need For Speed: Most Wanted (2005) - early 2000s yellow/brown tinted aesthetics aside, the game still looks good today and police chases can go on forever. Great fun.
Not a racing game, but a honorable mention: American/Euro Truck Simulator 2, bought it as a joke back then, but it does feel cathartic at times.