The short answer is that he's not. Amir is the protagonist of Khaled Hosseini's The Kite Runner , but he certainly does not portray the most heroic characteristics. The reason why Amir is the "hero," is that it's more interesting for a reader to follow a flawed character than...
The short answer is that he's not. Amir is the protagonist of Khaled Hosseini's The Kite Runner, but he certainly does not portray the most heroic characteristics. The reason why Amir is the "hero," is that it's more interesting for a reader to follow a flawed character than a great one. When we read a book, we mostly do it out of a desire to go along with someone on a journey. As a result, protagonists are often people who are missing something, which in Amir's case is confidence and redemption.
When you compare the two characters, Hassan absolutely comes off better and more suitable to be the hero. He is kind, loyal and strong; whereas Amir is a petty, cowardly person who struggles to stand up for what is right for most of the novel. Therein is the answer, however. Hassan is already at the end of his character development as the story begins. He doesn't change a lot, with the exception of becoming sadder. Amir, on the contrary, is only at the beginning, making him the logical focal point of the tale.
On the other hand, you could argue whether a true hero is someone who is born good or someone who becomes good through their own efforts. Hassan is an example of the former: ever since he was a little boy, he always followed his conscience and never allowed the unfair society to tell him otherwise. Several times throughout the novel, he is shown to be brave in situations that would daunt others, but Hassan never even thinks of shrinking back. Amir, by contrast, becomes the latter type of hero. Being self-preserving and selfish at first, Amir grows into a man who puts his own life on the line to save Hassan's son. In a way, then, Hassan never strays from the good path, but Amir is the only one who actively makes the choice to "be good again." Everyone might not agree, but that is definitely an argument you could make for Amir's case as the true hero of the story.
In a more general sense, Hassan is the true hero of life, but Amir is the natural hero of a novel.