Very well done, but lacking a strong storyline
On the contrary of the first movie, IA2 relies on more characters and their relations. The big success of IA1 has clearly brought the concept to another level. It's not only one movie with a simple concept here (two moles on opposite sides). But it's rather a crime saga comparable to the Godfather. If the intent is of course praisable, the result isn't 100% convincing. Too many little stories, too many characters, too many key scenes, the efficiency of the first movie is lost here.
This lack of a strong story line in the middle is maybe the only problem. Otherwise, everything is well done. Andrew Lau and Alan Mak's directing is good and efficient, without too many stylish effects. The music is solemn and fitting well with the "saga" tone. The technical aspect is also very solid. And of course the cast is impressive. Eric Tsang and Anthony Wong keep on delivering very strong performances, while Carina Lau brings a touch of grace and charme. Edison Chen is significantly better than usually, and Shawn Yu confirms that he could become an actor to remember. While in the work of Edison it's hard to see the future Andy Lau, Shawn Yu manages to build a very credible young Tony Leung. And of course, Francis Ng brings some of his unlimited intensity to his character.
The script of Alan Mak builds a lot of relation between those characters, maybe too many. There are probably some incoherences with the first movie. But such a work on the characters is quite rare in Hong-Kong, so it shouldn't be too blamed. It's just that IA2 gives the feeling to be a movie building something for a sequel, but this sequel has already been released, killing the concept of a progressive saga. There are still some very nice scenes (the murder of the 4 big bosses, the final), but the intensity is just not as high as for the first movie.
IA2 is surely not a masterpiece, but it's a very solid introduction to IA1. I would strongly recommend to people who didn't watch part 1 yet to begin by part 2, then follow with part 1 and the future part 3 (with the hope that this one will mix the qualities of the first two movies). For the moment none of the IA are perfect movies, but they are symptomatic of the new spirit in HK cinema: no more cheap photocopy of a successfull idea, but rather movies achieving a good balance between story, actors and technical qualities. Let's wait for part 3 to be able to judge this saga now. In the present circumstances, IA2 is a slightly disappointing prequel, but still above the usual standards in HK in many aspects.
Godfather-like failure
Instead of offering bad photocopy of Infernal Affairs, its creators tried with this prequel to compete with American mafia epics such as the Godfather. But they were probably aiming too high. The fact that the story is taking place during a long period of time, the will to add a political dimension to the story -the handover-, the multiplication of characters, the Nino Rotta like violins, thez Opera like passages of the score reminiscent of Casino, the will to refuse most of the time the video clip influence still present in the first part in order to try to shoot the movie in a classic, epic way, all of this means trying to compete with Scorcese and Coppola. But more characters means here too much characters for a two hour long movie, Edison Chen still lacks of charisma, Chapman To is overplaying compared to the general tone of the movie. The rest? Carina Lau, Anthony Wong, Francis Ng, Eric Tsang prove again their talent, Shawn Yu is correct and the score is sometimes unbearable. But the limit of the movie's treatment as a mafia epic is the fact that you can't borrow shooting and narrative choices so much linked with Americain culture (that is to say the American Dream, the foundation of America thanks to immigrants) without a minumum effort of adaptation of the material to the local Hong Kong context. In Casino, when a car explodes, a(n American) man's dream -of greatness and impossible love- goes up in smoke, in IA2 an exploding car is just an exploding car. And the movie tells us nothing about the consequences of the handover on the character's "intimate" life and on a "nation". The dialogues multiply definite sentences in order to make us believe that something great is happening. What? What made IA possible. That is to say what made an average cinematographic thing possible. So it's nothing great.