Last not least ... it seams to be our nature to expect unrealistic things from our chosen super"heroes". We create our Superstars - in sports, entertainement, politics - and expect that their next goal is at least as well achieved as the last one - OR BETTER. They are not allowed to fail anymore. When they do (and failure means not being on absolute top anymore) we blame and accuse them.
Getting better, doing "your best" all the time is a honorable principle. But when you have reached a certain level you cannot be THE BEST all the time. Others do the same, playing in the top range as well, and change is natural there.
But for some reason "change" is not accepted when it comes to the so called superstars. What we expect is a straight line pointing UP - getting better and better with each time. What it always will be is a curve with up and downs, even when the curve itself points upwards. But each "natural" down is considered a fail and media doesn't make it better. They seek for the next sensation only to feed their readers/viewers ... and there are more sensation seekers than superstars.
But even in this case there ARE plenty of superstars (real ones and shortly pushed ones) and the attention can concentrate on somneone else. And the real stars can get a break, recover, concentrate on a new project - and show up on top again. THE SUPERHERO on the other hand ... even when there would be a few at the same time would never be able to escape attention and this vicious circle.