We don't praise those who can kill the most, we praise those whose innovation -- or superpower -- allows them to do the most good. Thus, one can argue that society's change in ideals has accounted for the development of the superhero. Innovation, or having an ability that no one else has and the capacity to do good with it, is now seen as more valuable than having sheer brute force. In addition, the advent of secret societies instead of bragging rights can also be chalked up to a difference between classical and modern ideals. In classical times, heroes were in it for the glory, the honor, and the ability to brag about their status as a hero. Today, heroes are parts of secret societies were their identity is protected. In fact, in the humorous move the Incredibles, superhero parents teach their superhero children that their identities are their greatest assets, and the children should defend them. Once again, this can be explained by the difference...

The image of the superhero today is of one who undertakes bravery as a means of selfless defense of the innocent. A superhero who revealed his or her identity would become, quickly, a celebrity, as Peter Parker in Spiderman would surely attest. This would be in direct violation of the description of superheroes as selfless. Thus, since society's ideals have changed, embracing selflessness over bragging rights.
In sum, an easy way to decipher how a society's ideals have changed is to take a close look at its heroes. In classical times, heroes were bragging warriors, while today heroes keep their identity secret and try to prevent war. While the ancient and modern societies are rather similar regarding war, this can be seen as a change in social ideals. The hero adapts to mimic the social ideals of his or her culture, suggesting that the hero is often seen in a savior-like capacity.