>>36892546This list really highlights how much supplementary stuff that made HGSS better than GSC, but it also highlights that only relatively-minor improvements were made in HGSS. It still has many major problems that effect the main game: the gyms don't take advantage of the Gen 2 or Gen 4 pokemon, most routes and opponents are still low leveled, it has an inconvenient and limited rematch system inferior to FRLG/Emerald/Platinum's, and more Johto pokemon that were available in GSC were cut out or moved to Kanto.
In retrospect, HGSS isn't worth playing unless you're an avid Johto fan.