I think they have a lot of the same qualities. Idealism, compassion, generosity, courage.
My real life heroes are Gandhi, Ralph Nader, Franklin Delano Roosevelt, Mother Theresa, Oskar Schindler, and ordinary people who sometimes do extraordinary things like the men and women who volunteer for Doctors Without Borders and Habitat for Humanity. Writers and journalists who care passionately about getting to the truth and informing people are heroic in my mind. One that comes to mind is Edward Murrow.
http://en.wikipedia.org/wiki/Edward_R._Murrow
I guess the difference would be that the fictional ones might have superpowers so that they could be powerful enough to make the changes the world needs in order to be a better place for all of us to live.
Those who fight for what’s right and defend the weak, powerless and oppressed will always be my heroes. And those who speak out against injustice and cruelty. One example is those who protest the use of torture for any reason.
http://www.internationalnetworkforpeace.org/spip.php?article736
Here’s one fictional hero I like! Mr.Smith.
http://www.youtube.com/watch?v=zWyEc7FAMTg