Here's why this movie is good..
Up until the end of this movie i really didn't get it. I felt it was not impressive at all. But I did get it in the end. The strength of this movie is the hyper-realism. It's not some epic unbelievable story, or a story about some great hero. The protagonist is your average good person. He believes he should just work at the same job like his father and he doesn't make a commotion, not when his dad gets ill, not when he gets imprisoned just for having bad luck while driving, not when his girlfriend leaves him in jail. Even when his brother goes missing and the police are afraid of going into the gang territory, he still leaves things as they are. That's not very exciting but very very accurate. Only when the protagonist's brother dies(basically leaving him with no family) he decides to do something. He does not go crazy. He is the same person - who just got pushed until he came to the most logical conclusion. Not a very varied acting role for bale, but it's a very good portrayal of people's lives. A bit like a documentary.
The ending is also interesting. The protagonist is alone(having killed the cop or not? probably not). I imagine he spent more time in jail, got released and is now thinking back about his life. Was there something he could have done differently? Could have he saved his father or brother? And the bottom line is that he probably couldn't. He was raised into this type of life, abandoned by his country, there was not much chance for things to end up differently. And it's sad.