[carmad]

I started with GTR2, and had a good time with it, due to lots of mods which can be added on. Never raced online with it only against the AI which sucked.

I am a member of Iracing, and find it to be more realistic than GTR2, the physics are much better, the laser scanned tracks are excellent, and many of the real life pro racers comment on the cars and tracks being accurate compared to the real world. However, it is still a work in progress, if you want to drive lots of different cars the choices are limited, but new cars and tracks are being added every few months.
I have raced Solstice, Star Mazda, Radical and Daytona Prototype, and have progressed up the ladder from Rookie to B-licence, which has taken about 9 months.
Iracing is a subscription service, and costs about $13 a month, plus you have to buy extra cars and tracks, the subscription puts a lot of people off, but in my opinion, you get what you pay for. The racing gets better as you progress through the licenses, and is as intense and competitive as real life, much better than racing against AI. On the whole the racing is clean, and there are penalties for poor driving, and a protest procedure to weed out the persistent wreckers.
As in everything different strokes.