Sergeant York is not really a great film, but I have to admit I enjoyed it a little bit because how fascinating the true story is. The directing is fine, and the story is interesting, but the acting is the problem. Almost everyone plays everything rather dully. The only actor who really does anything with what they have is Walter Brennan who gives a nice performance as the local preacher.
Gary Cooper though does not give a great performance. York starts out as a rough housing shooting and drinking rapscallion. Cooper plays this part far too broadly. He just is that nothing else. He might as well be thug number 3 sense he is barely a character here. York begins to develop more but still Cooper plays him in a one dimensional way. Cooper never shows York as a man of great depth just a shallow shape of a character. There is a little enjoyment to come out of this performance like when he beats up a guy moving on his love interest, that was amusing, but he mostly does very little. When he suppose to seem angry he just seems slightly annoyed. His brash behavior just seems forced. His romantic chemistry with Joan Leslie is basically non existent.
Later when he finds religion very abruptly so there is no transformation phase you get another one dimensional portrayal. Now he is just an all around good guy, without depth or anything interesting about his portrayal. He is just boring as the good guy, and someone can play a good guy with more dimensions than he has here. He is forced to join the army even though he wanted to conscientiously object. He never seems to passionate about anything just rather dull. Then when he gets into the field he still seems rather dull and uninterested despite what he is doing. Cooper then has his big scene where he does York performs an almost unbelievable feat in battle. In this scene a friend of his is killed by a hand grenade. York quickly sums up all his anger and asks rather kindly who did that. Cooper just is always off with his performance. The real person certainly is interesting but you would not know that from Cooper's portrayal.