>>40502550music is probably the biggest part of it.
the speed of it makes it feel like you can run around and do anything without it feeling tedious.
and when I think of comfy, I think of the games i played after beating them the most. I think of which games i turned on and played just for the sake of playing them, even with no objective goal.
i put down most pokemon games after seeing all there was to see, but with bw2 there was a lot to explore and a lot of legendaries to catch (without them all being in the same place like in gen 6/7) so I just wandered around and did stuff. and even after catching all the legendaries i played the pwt and raised pokemon just because it felt fun, something thats a little lost on me for newer games.
this is mostly subjective though, i could see this all applying to hgss but i didn't play them till after bw2 so i didn't really have the same experience, i just transfered my pokemon to unova once i beat the game. i kinda wish i was nostalgic for hgss since silver is definitely my most nostalgic game.