Once the accessibility of NES games went away next generation, videogames started going back to being geeky and kids stuff.
Wait, WHAT?
Videogames were BUILT on Scifi and fantasy themed games. Only that a Nerd core audiance really appreciated or knew of.
Seriously, just LOOK at the boxart from back then.
Also Arcade was keeping the trend strong
It get into games back then, you had to be in sci fi, fantasy, or a japanese fetish (since most games werent translated even in arcades I remeber) Nes open the doors by making videogames something familys or anyone wanting there arcade games to enjoy (before the genesis or Mega drive to most the world) . This gen were trying our best to repeat last gen.