There is a healthy, and perhaps not so healthy, degree of cynicism in comics, and in society in general, but I think that comics have never strayed too far for too long from being optimistic. Most of the books are about heroes who save lives, often overcoming adversity along the way. But you need adversity, you need the dark times to appreciate the good times, to show how much the hero has overcome, to demonstrate the heroes inner and outer strengths. If the hero is never tested and wins all the time, what's the point? There's no drama there, there's no suspense. It'll get old real quick.
Exactly how are the younger generation more optimistic than a Gen-Xer like me? I think if Obama came along in the 90's/early 2000's, his message would've resonated among the young then too. A lot of people came out for Bill Clinton and even John Kerry because they represented, to some degree, a message of change and hope-esp. Bill Clinton's 1992 campaign where every other word he said was change, and the other word was probably economy.