I'd say you have a very vivid imagination and you can empathise and associate yourself with the film characters to a great degree. And while Ace Ventura's character is just too exaggerated and caricature-like, American Pie's teenagers are much more realistic which makes you feel what they would have felt in the portrayed situations.
My boyfriend is like that, he sometimes literally needs timeout during reality and reality-like TV shows (like The Office) when he feels uncomfortable for the characters. So you're not alone!
