Part of it could be attributed to the rise of blockbuster movies, but I think you also have to look at it in bigger terms than just that. Humanity as a whole constantly strives for bigger, better, faster, stronger. Our buildings get bigger, our computers get more complex, our special effects get more special, our sights get set farther, and our quest for longer life is a never-ending search.
It's not enough to have something because we eventually tire of that something and want something else. But we're not satisfied with that something just because it's newly made, we want it to be different and have aspects that make it more special than the old something that we put aside. Everything comes down to a desire to experience. The Grand Canyon is amazing, but once you've been there it ceases to hold that same sense of wonder that it once did. So the next summer we head to a different national monument, one that we haven't been to before and one that is, in some way, "better" than the Grand Canyon.
The same thing goes for videogames. We play one videogames and once we've finished, we start looking for something else. Gaming quickly falls into a cycle of bigger, better, faster, stronger and soon we demand that every aspect of the next new game surpass the old in order to satiate our deeply entrenched desire for that something else.
You could argue that nostalgia is evidence against this way of thinking, but I think it only reinforces what I'm saying. Nostalgia has more to do with the rejection of our current status and a desire to return to our own rose-tinted past. We want to try to recapture something that we once experienced a long time ago but, for some reason, can't experience in the present, either because that experience no longer exists or because we feel that analogues of that experience have changed to the point where they cannot elicit the same response. In this way, nostalgia is merely another form in which our desire to experience manifests itself in our life.
To put it simply, we don't want to keep experiencing again the things that we have right now. We either want to return to an old experience and try to recapture the original feeling or we want something new and special that can equal the impact of our past experiences.
