Marvel: It all began with the Fantastic Four in 1961 (with retroactive history in place, as occasionally dramatized). At the stroke of midnight, New Year's Eve 1977, the Marvel Universe split in two: The Normal Universe and the Corrupt Universe. Sadly, we have only been privy to the goings on of the Corrupt Universe. But in the Normal Universe, things have gone along as they should. The characters we know are now middle-aged to elderly (except for those who are long-lived or immortal) and have lived good lives. Some of the children of the superheroes have grown up to take over defending the Earth and the Universe, and have been joined by new heroes. Unfortunately, I have no way of knowing the details, but someday I hope to find the portal and catch up on thirty years of back issues.
DC: It's still the Silver Age. It will always be the Silver Age.