I wasn't directly comparing them, but those are the biggest market in the racing game world. All eyes are on them, and especially with the amount of physics work involved in FM3 and GT5 a comparison is inevitable.
I've never played iRacing (and I never will) and my experience of NKP ended when I couldn't redefine the controls (so I was stuck in 1st gear). But in terms of rF v LFS, I think it all comes down to the staff headcount, doesn't it?
Without mods, rF would be in an even poorer state than LFS is. Without releasing the finished product, ISI probably wouldn't have let modders near it. Without so many people working on it, rF would never have been finished.
I keep trying to argue against getting more people involved with LFS, but in terms of keeping it as a marketable competitor it's getting really hard! With minor mods like the hi-res textures, LFS can look really good, but with rF2 somewhere on the horizon maybe LFS is just destined to be one of those programs that has amazing potential but takes about 20 years to get there.
I love the feel of driving in LFS. It just feels right. No other racer has ever given me that "holy crap" feeling as I hurtle into a corner with tyres squealing. I've done the same thing in real life (accidentally on a narrow country B-road) and like to believe it was my LFS experience that kept me from ending up mangled on a banking. I refuse to become a doomsayer, I just love it too much