As with Mad Jock I have had a few trial flight punters land the aeroplane because they had enough co-ordination and spare capacity to listen and do exactly what I was telling them and when.
Once the aeroplane is in a stable approach it's just a case of saying 'raise the nose. stop. move the throttle forward. stop.' or whatever until they've got it in the flare. Some get the flare right, most don't. Fair enough considering most don't know what they're looking for. The difficult part with students learning to land unprompted is the development of judgement and rate of control and throttle movement relative to rates of descent and speed change close in to the runway. I've seen loads of people pick-up the first 4 or 5 hours of flying training very readily and then get bogged-down for hours trying to get the approach and flare right.
As far as natural talent is concerned, I've seen 40 year-old housewives with excellent co-ordination and spacial awareness who had no idea they had it, as well as a few driving instructors who couldn't even begin to grasp the concept of finesse with throttle and brakes while taxying. Talent is a random thing...
Back to the flight sim thing. I feel that it is best to go into flying training without too many preconceived ideas. Those that have several thousand hours in front of their PCs tend to have instrument fixation, poor lookout, and can be difficult to teach the fundamentals to. I do agree that it can be a valuable learning tool if used properly in a structured way, preferably after a student has done some real flying.
I once had the Mother of a 14 year-old boy complain to the flying school that I had not allowed him to land the aircraft on a trial flight, "even though he can do it on his computer at home"!
ST