Obviously I'm not including burnout as the fun in that is trashing opponent cars while you're racing; for myself I enjoyed some of the earlier entries in need for speed (never played the later ones) cause I could crash into other cars and knock them off cliffs and beat them around to give myself an advantage; I just don't know what draws people to say for example Gran Turismo vs.....I don't know, I don't know any other racing games. Other than the 'crashing into other cars' factor, I don't know what the draw to one racing game vs another is.
Honestly, to the layperson when it comes to what the most realistic racing simulator is, it doesn't really matter. Some real life drivers have complained about iRacing's physics, but at the end of the day, that's where the majority of the competition is, including real life drivers.
To me, there's also a pretty massive difference in various arcade/less realistic games. Daytona USA, Sega Rally and Burnout 3 are all going to feel completely different to each other, and all three of those are some of my all time favorite games. It just depends of whether the focus is on wrecking other cars, racing other cars or trying to get through a route as fast as possible, all of those are going to feel different and have completely different objectives.