I too know someone who fits exactly the description above - talks as though it's real ('bad weather last night in Delhi' etc) and I find it excruciatingly embarrassing. He also insists that it increases flying proficiency (he may even log his 'hours' for all I know). I can scarcely think of a more dangerous delusion for a wannabe - as some of you have mentioned, it might assist in a couple of very rudimentary aspects but basically thinking that a joystick connected to a PC bears any relation to flying an aircraft is a good way to get yourself killed. Scary stuff.
And no, I have never seen a professional pilot land an FS game. Especially that f***ing Learjet.