Atticus manages to distinguish himself from other people in Maycomb because of his unselfish behavior and a dogged desire to treat people in a fair and humane manner. He is not oblivious to evil nor does he see only good in all people. He is quite aware of many of his neighbors' shortcomings--particularly Bob Ewell, in whom even Atticus sees little good--but Atticus has the extraordinary ability to downplay their downsides, instead focusing on the rights of every man to be different. Through Atticus' eyes, things such as age, race, gender and social standing have little significance. As a neighbor, Atticus has few peers, and he is always willing to lend a helping hand--whether as a friend or legal representative. He proves to be a friend of nearly everyone in the town, but he is more than willing to forfeit some of his good standing with others if the cause is just (defending Tom in the rape trial). By his actions, he passes down these virtues to his children, who recognize his inherent good and fairness. Atticus proves to be a hero by the difficult decisions he undertakes and the manner in which he carries them out.
In a time of overt racial tension in the South, Atticus Finch is one character who seems not to be a "product of his time." Atticus's pursuit of justice, his unwavering sense of equality and fairness, and his mission to teach his children to respect all others regardless of their race, socio-economic status, and gender make him an exceptional character in literature.
The term "hero" can have many different definitions, but if we consider a hero to be someone who is courageous, who fights for a cause, or who serves as a model citizen for others, then Atticus certainly can be defined as such. (Interestingly, the American Film Institute dubbed Atticus Finch as the number one greatest film hero in 2003.)