>>465869698 bit sound fonts tend to age better than low-quality midi ones (RSE aside, somehow those strings and trumpets still work for me). Add that with the sound fond they used generally having a warmer, more "fuzzy" or "muted" timbre, and the GSC ost trumps HGSS easily. Case in point, even on the new route in HGSS the GB track they wrote for it sounds incredible, while the DS track is fine.
https://www.youtube.com/watch?v=w2O3-Xk_gXEhttps://www.youtube.com/watch?v=LHxE6JjnSd8This applies to the ost too, but graphically there was also much more in the way of limitations that they had to work around on gbc than on ds (4 or 3 color pallets, gbc resolution, etc.), and the solutions they used to still convey the pokemon, characters, and locations in spite of those limitations become part of the charm of the art as well.
