All joking aside, something I love about Ruby & Sapphire is Game Freak obviously got told, "Hey, look at the cool visual tricks you can do" and then delightedly put every single one that could fit in the game, stretching and squashing sprites, throwing in weird backgrounds and cool animations for attacks, even stuff like reflections in water. Things that wouldn't have been possible on the GBC, and they got to play with them all like a kid on Christmas.
I think that love really shows in the finished product. At the risk of sounding like an old fart, Gen III on GBA might also be the true "classic" look for the series.
