I like rfactor and LFS. The others I haven't tried so I can't comment.
My question for Tristan is this... How long has it been since you tried rfactor? I agree that the physics aren't as good or even close to LFS, not by a long shot but.... the variety is awsome!
The reason I ask how long it has been since you tried it is, I play with some people that tried it awhile ago and didn't like it at all. Then after trying it recently they have changed their opinions.
It definitly took some time to get the wheels setup and such, and to get the same tracks, and to get a server going, and to connect to it, and not to get an error

, but after all this was taken care of it is a fun game!!