The real "ever-present time capsule that we can re-enter at will" is the internet, which reignites our memory of the past so immersive. As video games go, for me, they're a product of that past, similar to films or books. As such, they have an objective quality and that's the more decisive reason, why we're attached to it.
We don't read Victor Hugo's Les Misérables today, more than 150 years after its release, because of nostalgia. We do it, because it has qualities that allow us to understand ourselves, to confront past times and make connections to present ones. And yes, to be entertained, too. It's knowing our roots, it's knowing who we are.
A lot of games got the same careful treatment by their creators as top rated literature or motion pictures did. This huge and intensive amounts of time invested in their creation are the main reason for their longevity. Now we take trips down the digital memory lane of the world wide web and remember that timeless quality.