How do you determine the difference between a racing simulator and a video game? I've come up with a simple test, if you take a hand controller, like an Xbox controller, and you try to drive a simulator it will be nearly impossible to drive. You need to be able to create more precise and exact controls to really race and feel the car.
Now I want to be clear, this isn't to say you can't have fun in games like Forza and Need for Speed, but if you are going for a true to life racing experience those aren't your best options.
Dirt Rally 2, a wonderful game to play on the Xbox seems too easy, the car almost too stable. It is the same with Forza, all the cars feel and drive very similar to each other. Now the exception to this may be Grand Turismo 7, but from what I have read it is still lacking in the track details and information that comes from the car as you drive. In the video below Boosted Media compares driving with a wheel and pedals to driving with a hand controller back to back.
What is your goal? We use Assetto Corsa on our simulators, mostly because it is a pure simulator, and it looks the best. When I tried driving AC on my Xbox without a wheel or pedals I wanted to throw my controller through the window. So if I didn't have a racing simulator set up I would never play it.
We run iRacing and Assetto Corsa on our setups. I love them both, but they are different. Assetto Corsa looks better than any simulator you will find, and that is not really debatable. However if realism is your goal then you would likely want to go with iRacing. This is just my opinion, and I am just a 4th grade teacher so take it with a big grain of salt. But, from everything I have read and watched with real life drivers iRacing translates best to on track skills.
iRacing doesn't look as good, and it requires a monthly subscription for each driver. On top of that it get's incredibly expensive if you really want to get into it because you also have to buy individual cars and tracks.
So, you just have to decide what is right for you. I know guys that have really fancy simulators and love cruising around in Forza! Other guys get really serious and end up in endurance leagues racing for hours at a time.
PS - if you're interested in driving and really learning to race hit the link below and learn how you can get 4 hours of racing free by joining our 28 day driver transformation challenge.