Most of which s-cked and WERE laughable! The same can be said of many more recent war films however (Born on the Fourth of July comes to mind).
The best war films are either not directly about war (ie Apocalypse Now) or those that don't hide the grittier aspects of war while not making knee jerk statements either way (We Were Soldiers comes to mind). Those WWII movies with the Andrews Sisters or John Wayne had laughable scripts and were as believable as the Wizard of Oz.
John Ford's 'They Were Expendeable' with Wayne was quite good though.