In answer to the question "How do you interact it with real flying?" I have to say I don't. The main thing that I love about flying is the physical feeling that you get when you and your aeroplane are moving in three dimensions. Not necessarily chucking yourself around the sky, but you do feel yourself moving around your own three axes to an extent. I love that. No matter how good a flight sim's graphics and sounds are, there's no way you can replicate that feeling, that sense of actual movement, when you're sitting in front of a pc.
That said, I do think there's a lot to be gained from flight sims; I own a copy of Combat Flight Simulator, and there is something quite satisfying about waking up on a non-flyable winters morning, powering up the pc, and taking out my weather frustrations by using a Spit IX to give a bunch of Me109's the good news.
And additionally, my seven year old son loves to have a go at being a Spitfire pilot too. Although I dread the day he challenges me to an interactive dogfight, he's getting a bit good...
The thing is though, it's a break from reality. Nobody in their right mind is going to hand me the keys to their Spitfire and say 'off you go old chap, just don't bend it...' so that's why I enjoy regressing back to being a kid again from time to time.
Just my twopenneth...