Pepe le Moko

Pepe le Moko is a 1937 French film starring Jean Gabin. It's based on a book by the same name. It was remade as Algiers starring Charles Boyer and Hedy Lamarr the following year. This is very watchable (and re-watchable), with characters you care about. I've seen it before, but I'm always up for another.
trailer:

The book 1001 Movies You Must See Before You Die includes this film. Empire Online has this verdict: "Populated by fascinating characters and with a tough sensibility, this is pulp noir at its finest — and way ahead of its time." Time Out says it's "A touchstone film for cinema historians". DVD Talk calls it "a classic" and "very influential". Films de France says it was "so depressingly grim that it was banned by the French government at the outset of WWII through concerns over its demoralising influence" and calls it "a major cinematic achievement" and "French film noir at its most vivid and intoxicating". Rotten Tomatoes has a critics score of 100%.