My first and only legitimately fully completed Pokémon game, and to this day still stands the only reason that generation 3 is my favourite Pokémon generation.
It's amazing, a huge upgrade to ruby and sapphire, some of the exclusive Pokémon were taken out and both teams were included. This meant more team variations, harder foes, and rivals teams that included a much more wider spread of Pokémon so that the players own team must include a wider spread of types.
The game starts of slow with a lot of grinding and new mechanic learnings. However things quickly uprise as teams magma and aqua make the skies roar as the player takes a quick turn from completing the Pokédex to stopping total domination!
After the first 2-3 gyms the protagonist must venture and explore new caves, mountains, cities treetop villages, science labs and so much more in this new region. Near the endgame the player will receive new challenges and Pokémon ready to set off for victory road only to see a nice surprise in addition to the original games.
The sense of achievement in this game is amazing, definitely the number 1 selling factor even the after-game is amazing, all new legendaries, areas to explore, hidden secrets, and an international Pokédex along with new starters and Islands.