Everytime someone drops by my house and sees the steering wheel mounted to the side of my desk, they immediately want to drive. I always put them in a formula trainer with all helpers and it still takes them a while to just keep the car on the track.
I've driven formula trainers at Skip Barber Racing School and the trainers in rFactor are very similar. Obviously no simulator is going to match the real thing, but rFactor is very challenging and luckily is a lot less painful when you make mistakes.
Here are a couple of videos I stumbled upon. Each shows a side-by-side of an F1 car and an rFactor F1 car around a complete lap of a circuit. Not saying these guys are on par with Michael Schumacher, but the realism of at least these two tracks is fairly apparent. And just to note, I still don't drive the F1 cars in rFactor. Just too fast for my skill level.
Found Video: "rFactor(CTDP F1 Mod) Vs Real F1 - Monza Circuit"
Found Video: "Comparison ME vs. Michael Schumacher" at Imola