Oldboy (2003)

The 2003 Korean film, not the 2013 American remake. Park Chan-wook took a Japanese manga by Garon Tsuchiya and Nobuaki Minegishi, kept its brilliant hook of a businessman locked in an ordinary room for fifteen years without being told why, and built something far more operatic and cruel around it. Choi Min-sik is ferocious as the man let out to find his jailer, and the film won the Grand Prix at Cannes in 2004. It is the strongest argument on this list that an adaptation can outgrow its source. Be warned that the violence and the final revelation are hard to shake.