Though i appreciate your thought pattern and respect your opinion, i can't say i agree with it at all. There's never been an essential video game to play which appeals to every gamer; That implies universal appeal, and that doesn't exist. I agree that genres have diluted over time with design aspects that were once set in stone applied to genres which did not have them. But i can still make you a list of must-play JRPGs. Street Fighter II was massively superseded by its variations, of which Super Street Fighter II Turbo Edition is a fantastic fighting game that is definitely awesome to play today.
I've read your post carefully multiple times, but i think i don't fully understand your point. We can effortlessly make lists of must-play video games within the confines of their specific genre just fine. But they are fundamentally subjective. Maybe some examples will overlap with my examples, maybe not at all. For example, i am not a Dark Souls/Dark Souls Clones fan, at all. So i will not recommend it as a must-play, at all. You may, because maybe you've enjoyed it tremendously.
Eh, outside technical aspects, saying a video game "hasn't aged well" is like saying my favorite color is better than yours; meaninglessly subjective and a useless, vague dismissal of a game. I've become acquainted with a 13 year old gamer on youtube a while back who collects ATARI 2600 video games. He is obviously not doing it because he's nostalgic, neither did his father play the ATARI 2600. He's doing it because he is a collector and appreciates video games based on the time and system they were made for.
Besides the historical preservation aspect - which alone will never let classics be forgotten - a hobby like this will always have its passionate fans that dig deeper into video game history and find something else to play around with that's not "hip and new". Acting as if video games are a popularity contest and using them like "fast-food" (one and done) isn't such a widespread thing. Especially not in the PC Gaming sphere where great video games usually attract strong communities that keep video games alive and relevant - for example, and i only need one example - the original Doom and Doom II. Still has a remarkably massive community around them, and they're over 25 years old. Never mind official remasters and remakes.