When people like to see a film more than once, there is usually aspects of the film's content that they feed off of similar to a favorite meal. it could be something about the cinematography, music, costumes, characters, particular scenes even etc they happen to like besides the plot/storyline. This is why some movies are just one-offs where once you know what happened from a to b, you are done as in been there and done that type of view.
It can also be subtle such as the type of film such as campy, creepy, funny etc. Every film has it's own texture, nuance and style, if you will. I notice i like to watch different versions of agatha christie's 'and then there were none'. Besides the story, i like the setting, period piece and mood etc. I also like the old hammer films as it has it's own brand of nuanced nostalgia to me and appeal. Every christmas, i can watch the christmas carol and it never gets old because it has a charm and classic timeless message etc. Just as most slasher films you will not want to watch more than once unless it has a certain appeal to it or nostalgia to you. for instance, though i don't like slasher films such as hostel etc, i can watch nightmare on elm street more than once occasionally because it's kind of iconic to me, in a 'if it's on and nothing else' i will casually watch it etc.
So if you see a film as a work of comprehensive art, films will have a character of it's own and you may like to view it multiple times similar to tasting a good wine or viewing a picture that appeals to you.