"Silver age" is, after all, just a concept. So here are some worlds to put behind it, to get a feel for the setting, for the kind of character PCs are.
Heroism is, basically doing the right thing. It's hanging on that moment longer, protecting the innocent and serving others. It's about the kind of people who would be heroes even without powers, because they are kind and decent people.
It's about character. Honour. Integrity. The responsibility of being role models as you are, the weight that goes along with that -- of accepting it, but never giving into it, because you are needed. Even if you're hated, or feared, or people turn against you, you don't stop -- because it's about doing what is right, about being a hero no matter what the odds.
It's not taking leaps off the edge of what you know, but standing there to face the darkness, stare at your own demons if need be, and draw a line in a sand. And say to it: "No further. You will not come this point." And standing, and holding it back, if only for another day.
It's about optimism, and the future, and love, and hope, and all those values that are harder to hold to now than they were in the silver age but more important than ever. It's about the possibility of redemption, and the power of compassion.
Because the world isn't Us and Them. It's ALL us, even the ugly parts people don't like to admit. People need heroes, for much the same reason they need gods: to help them believe the world is truly the wonderful place it's advertised as being. And while you can't be everywhere, can't do everything, you do what you can and hope it's enough, sacrificing to a cause greater than yourself, to humanity, because people can be good ...
and because, of all powers, the one that truly matters is hope.
