Pokémon Emerald

Pokémon Emerald is like the "Pokémon Yellow/Crystal" of Ruby/Sapphire, meaning that it has most of the Pokémon (not all). And also since it was the third of the generation to be released. So it has better features than Ruby/Sapphire (features like better Pokémon graphics and stuff. Like Pokémon Yellow has Pikachu following you and the Pokémon look like they are supposed to. Pokémon Red's Pidgey looked like a sparrow.)