There are many more films about World War II than there are about World War I, but there are still many notable films about it. World War II, with its very clear villain in Hitler and its definitive victory over evil, is often the more compelling subject. Films about the difficulties of trench warfare are not so easy to sell, perhaps, but there have still been some masterpieces about "the war to end all wars" as it was called by many at the time.
Acclaimed films about World War I include A Very Long Engagement, directed by Jean-Pierre Jeunet, White Ribbon, directed by Michael Haneke, All Quiet on the Western Front, directed by Lewis Milestone, La Grande Illusion, directed by Jean Renoir, Lawrence of Arabia, directed by David Lean, Charlie Chaplin's Shoulder Arms, Howard Hughes' Hell's Angels, and Stanley Kubrick's Paths of Glory.
All these films depict different situations surrounding the war, from the wives left behind to Australian participation in the war to real-life British archaeologist and army officer T.E. Lawrence. Many have already added 1917 to this list of great films.