For a serious film, I would like to see a really good version of Somerset Maugham's "The Razor's Edge".
Alistair McLean's best book by far, "HMS Ulysees" would have to make a good movie. CS Forester's book "The Ship" is also full of strong characters and has the potential to make a great movie.
Dennis Wheatley was a right wing loony of very little literary merit, however,his books - especially the Roger Brooke saga - were very entertaining and have plenty of suitable material for blockbuster movies. Trouble is, only an American company would have the resources to make one and Roger Brooke with an American accent is not a prospect which is likely to lure me to the cinema!