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Have you thought of indirectly asking him what films he likes/wants to see? You could start the conversation off by stating some of the films you are/aren't interested in and see what he responds with. If he responds with what films he likes/dislikes it'll certainly give you a good indicator of what film you could consider getting him.

Secondly, don't limit yourself to just giving him a gift, why not take him somewhere? Take him out for a small meal and offer to pay, or take him to the cinema and let him be the one to choose, or if you've found out what he really wants to go see beforehand, book the tickets in advance to make sure you get a good seating position, sneak in some popcorn and you're away.