Overview  From the director of The Killer, the first two could be considered as a single entity although they're sharply different in style. The first concerns a gangster trying to keep his 'career' secret from his policeman brother and gain revenge for some treachery, helped by hitman Chow Yun-Fat (HK's answer to Rutger Hauer). It's mostly solid, if slightly earnest, drama, that swings wildly from splatter to soap opera.
It was enormously successful in Hong Kong, so naturally led to a sequel. Problem: Chow Yun Fat was blown away at the end. Solution: he had a twin brother in New York, who's dragged in when a friend, trying to go straight, is framed for a murder. Cue a Taxi Driver impression, a perfect mix of melodrama and tension and an awesome final 15 minutes, with more corpses than Highgate Cemetery, to which no description can do justice. This is Hong Kong cinema at it's very best - go down your local Chinese video library now and beg them to give you a copy.
Tsui Hark's entry is a prequel to the first two parts, set in the last days of Vietnam; much of the film gives the impression of being shot in slow-motion, it's stately and graceful, with the obligatory mega-kill finale. The three movies virtually define the 'heroic bloodshed' genre and should ideally be viewed in one session, as otherwise it's easy to lose track of who's taking revenge for who, on who...
7, 10 & 8/10
A Better Tomorrow. There's one aspect of the first entry that now stands out like a sore thumb; a hideous score, which is inappropriate when it's not downright awful. It says quite a lot about the film that the performances are largely capable of making you forget this side. I had forgotten that Chow is really a supporting actor in this film, which is more about the two brothers played by Leslie Cheung and Ti Lung, and their relationship. Still, almost all the best moments belong to Chow, whether you mean his pot-plant assisted assault in a restaurant, or sitting motionless in a temple, with a cigarette in his lips that's almost entirely turned to ash. But credit also Waise Lee for his villainous turn, essential as a foil. 
A Better Tomorrow 2 Contrived? Sure. Melodramatic? Undeniably. Ludicrously OTT action? Without a doubt. But the sheer commitment shown by everyone involved - certainly, not least Chow Yun-Fat - drags the viewer along by the scruff of the neck, by pure force of will. Is it meant to be taken seriously? I'm not sure: while Ti Lung and Dean Shek are straight faced, there are times when both the makers and Chow seem to be winking at the camera. Witness the latter's amusingly overblown first scene, which might be the best acting he's ever done - or might be the worst. Hard to say, really. He ends up bonding with the near-catatonic Lung (Shek) and helping him survive and regain his sanity, before returning to HK for a jaw-dropping gun-battle against every bad guy this side of Shanghai (the body count is 89, I believe).
There's some debate over how much a Woo-film this is, save that final battle; Tsui Hark edited much of the film, wanting it to be more about Lung, which may explain why Ken (Chow) doesn't appear until more than 25 minutes into the film. This shift in focus does hurt, but stylistic considerations aside, it's a solid action flick, deftly weaving together the themes of redemption, loyalty and family ties. There are some plot elements which don't actually make much sense, and the decision of the trio to seek their revenge in the form of an all-out, suicidal assault is never adequately explained. However, the end result is one of the icons of the genre, an adrenaline-rush of almost unparalleled ferocity, that encapsulates exactly what this kind of cinema should all about.