Infernal Affairs earns its place on this list not just because it's an amazing movie, but also because it's responsible for Scorsese's The Departed. Yeah, that's right, The Departed is actually a remake of Andrew Lau's film, and was as critically acclaimed (if not more so), than Scorsese's eventual remake. The film's plot is essentially identical to Scorsese's adaptation, only with certain cultural differences i.e. the Triad replaces the Irish American Mob and the film isn't set in Boston like Scorsese's version. The film was not only almost universally adored, but also breathed new life into Hong Kong's films industry, having been on its way into a sharp decline beforehand. Praised for its original plot and concise, swift narrative structure, Infernal Affairs reiterated that films don't have to be a product of Hollywood or English language to gain international recognition. If you're a fan of The Departed, then Infernal Affairs is a must see, not only so you can see the differences between the two films, but because the original is different enough to warrant your attention.