The Pokémon Peninsula > Pokémon Emerald
Emerald is the follow-up to Ruby and Sapphire, like Yellow and Crystal, and it's extremely cool. How cool, you ask? How about Mew, for a start? You need a special ticket to get to it, but yes, it's catchable! Plus, you can get a heap of cool Pokémon and legendaries without trading - like both Kyogre and Groudon, for example!
Emerald is for the GameBoy Advance system, meaning that it will work on GameBoy Advance and above only. To catch all possible Pokémon and complete the Pokédex, you may need to trade Pokémon using a Game Link Cable between two players.
Pokémon List (available/unavailable)