The Good: One of my favorite films of all time. Having been obsessed with gangster movies since I was a kid, there really is nobody better than Marty Scorsese. I actually saw, and fell in love with, Infernal Affairs before Scorsese remade it and I love the direction in which he took it. Fantastic script, incredible performances, and an ending that makes me infinitely happy.
The Bad: Some people might think it's too long, I do not.