As a WWI and II researcher, the films tend to watch over and over generally are made about that era:
'Went The Day Well?', 'Coastal Command' (film I obtained from the IWM photographic and film dept), 'London Can Take It'... probably one of my favourite films, even though it is only about 9 minutes long. It was produced for the US market about real people in the London Blitz. Distributed by Warner Brothers, it was shown in over 1200 cinemas across the US.
1996 WWI shell-shock film called 'Regeneration'. It's very much in the mould of Spielberg. Based on a Pat barker's book about the first meeting of Wilfred Owen and Siegfried Sassoon, it follows Capt. Rivers, played by Jonathan Pryce, and his humane treatment at Craiglockhart hospital near Edinburgh.
Watch from 5 mins 24 seconds...
2004 three-part docudrama of Dunkirk, written and directed by Alex Holmes. This three-parter puts the 1017 Nolan film in the shade. This is based on real people who were there. Very hard-hitting pic
Others I don't object to watching over and over is: 'The Ladykillers' (original, starring Alec Guiness); 'Brief Encounter', with Trevor Howard and Celia Johnson; 'Brighton Rock'; 'The Italian Job'.