My two cents worth: In a time when all the live action Disney movies seem to be a variant on "I was normal but just discovered I am/have just been mistaken for royalty/merperson/rock star/leprechaun/etc., this movie from the 1980's is a real breath of fresh air.
The scenario, waking up and discovering that everything except you has changed, and knowing you'll be somebody's idea of a guinea pig for the rest of your life, is instantly relatable and creepy, whether you're a kid or an adult. The kid fainting, the change in the two brother's relationship due to the age flop, parents trying to protect their son, government trying to exploit the kid's knowledge, everyone's reactions to the situation are all logical and believable.
And who hasn't wanted a chance to fly a saucer? Having Max, the ship's pilot, be a robot was another stroke of brilliance. So many movies have the aliens flying all the way here to come visit us face to face. But if we send machines to other planets because it's cheaper than going ourselves, why wouldn't they? And having him learn about Earth courtesy of a 12-year-old's TV polluted brain was hysterical.
The movie seems a little dated today; but it's forgivable because, like Back to the Future, it's set so specifically in a certain frame of time (you expect it to look and sound like 1986 because, hey, they keep telling you that's when it is.)
Recommendations: Back to the Future and Big are the two I can think of that are most along these lines.