I am slightly jealous of Amores Perros, because it has a story setup similar to one I have long thought of using: taking a tragic traffic accident, then telling the stories of all the previously-unconnected lives affected by it.
Here we have three victims: the first a punky teenager who enters the world of dogfighting in order to raise the money to run away with his abusive brother's pretty wife; the second a fashion model who must deal with the accident's physical aftermath on her once-perfect body as she searches for her missing dog; the third a homeless hitman who cares more for his stray dogs than for the people he encounters.
If you're sensing a "dog" theme across the three stories, you are correct, and indeed the film's title translates into "Love Dogs" (or the smirkier "Love's a Bitch", the film's official English title). Iñárritu seems to be after some metaphor with his dogs, but it never quite becomes clear just what they are meant to symbolize.
Well-acted and extremely stylish (with that now-common "documentary look": handheld camera, washed-out colors, frenetic editing), Amores Perros is still ultimately shallow. Iñárritu seems to believe that a grim film is an important film. But life – even amongst the downtrodden – is filled with more hope and humor than this bleak melodrama suggests.
There's also a sense that Iñárritu – a successful DJ and music video director – finds it necessary to maintain his street cred, so he paints his middle-class characters as vain, dishonorable creatures who deserve their comeuppance, while displaying a Tarantino-like sympathy for thieves and hitmen. (Note to my fellow indie filmmakers: can we please take a break from filling every freaking movie with hitmen?) But I'll bet Iñárritu has a lot more fashion model friends than dogfighter friends.
Speaking of which, although there is a disclaimer at the start of the film that states that none of the dogs used were hurt in any way, animal lovers may want to avoid Amores Perros for its unsettling number of bleeding and/or dead canines.
The film is well-made and has a fine soundtrack. I just wish it actually had something meaningful to say.