#49 at time of writing.
Martin Scorsese's remake of Hong Kong gangster flick Infernal Affairs is epic, powerful, and only occasionally indulgent. There's a terrific cast (although it's tempting to imagine an alternative universe in which Pacino and De Niro 20 years ago starred), and a fantastic set-up: a gangster mole in the police force and an undercover cop in the gang are both trying to find each other out.
The tension is kept sky-high, the plot has more twists than a candy-cane, and the acting is second-to-none. Both the critics and the box-office loved it: It won the Best Picture Oscar (the movie with the most uses of the F-word to do so), and it's the highest-grossing Scorsese film.
A small gripe - I don't normally spot continuity errors, but it is hard not to in this film; there are little bits of sloppiness everywhere.