I mean, just explain it.

You can fairly easily make someone understand why something was instrumental to the creation of something else. Or why it holds so much value to you.

What you can't do is make them share your personal nostalgia or personal emotional investment in it...they didn't live those experiences.

And to be honest I don't get why we put games on a pedestal just for being important in their day. I can acknowledge that Wolfenstein 3D was very important for the development of FPS games...while still thinking it sucks ass as an actual game.