The jump from Game Boy to Game Boy Advance was truly an outstanding leap in Pokemon. Playing a game in the region of Hoenn after one of the Johto games feels like the developers had so much more they could work with, and it shows. Many of the problems in Gen I & II are now gone (though not all: the endgame level curve is still steep, the type diversity is better but still not fully there especially re: Steel type), and the game has more diversity in types of routes, now including a desert and a volcano! Though this game loses the branching that Pokemon had been known for up to this point, the story is legitimate and the dungeon quality ranges from decent to very good, with the only complaint being how many HM moves you need to know in victory road.

I really think Sapphire (and Ruby, also) is a great game on its own merits. It's a bit of a shame that Emerald is just Better, and you really do feel that when going back to Sapphire, but I'm basing my judgement on this games own merits, not that "it's not Emerald", especially since Emerald did derive from Ruby & Sapphire.