Exceptionally high drama for its day, this tragic, tragic tale can tend to drag, but it's one of the best examples of well-realized filmmaking from the first half of the 20th century. Josef von Sternberg tells the story of a crusty professor (Emil Jannings) who discovers his students are frequenting a nightclub to see one Lola Lola (Marlene Dietrich). Determined to stop them, he goes to The Blue Angel himself, only to find himself instantly smitten with Lola. Ultimately he quits his job, marries Lola, and lives off his money until they go broke. He ends up becoming a clown, facing his most humiliating moment when he returns to The Blue Angel to appear on the stage. Heartbreaking to a fault, Jannings owns the show over the more highly-touted Dietrich; you can almost see the sadness oozing from his pores.

Aka Der Blaue Engel.