Infernal Affairs (2002)
It is impossible to watch this movie and take it on its own merits – you have to compare it to “The Departed”. Interestingly enough, given that these two movies have the same plot they are very different – focusing on quite different themes in the story. Infernal Affairs is more concerned with the effect that leading double lives has on the protagonists while The Departed investigates the theme of deception and misdirection more. Both well worth seeing.