Pok�mon Emerald is the third game set in the land of Hoenn. On first looks this game seems to be identical to it's predecessors, Ruby & Sapphire, however there is much more that meet's the eye in this game
First thing you'll probably notice are the Pok�mon's Animations, similar to how they were animated in Crystal, which are making a welcome return to the Pok�mon games. Also, the graphics in this game are sharper than in Ruby/Sapphire with more detail to the overworld
Both Team Aqua & Team Magma are heavily involved in this game's storyline as they both try to awaken their respective Pok�mons...and when they do, thats where the game radically changes from the other games with a whole bit where they battle and you have to stop them.
There is also inclusion of many new areas including Magma Hideout, Mirage Tower, Desert Underpass, Marine Cave, Terra Cave, Studio Cave & finally and most importantly, the Battle Frontier.
The Battle Frontier contains 7 buildings which all incorporate a different style of battling where you have to battle through multiple trainers to get to their leader's, The Frontier Brains. These battle styles include Rental Pok�mon, Random Rooms, Relying on your Pok�mon's Nature to battle, Tournements and many more...definitely a way to challenge any trainer
The Gym Leaders & Elite Four have also been updated with different Pok�mon and a whole new gym leader! To make things even better you can rebattle the Gym Leaders up to 4 times via the Match Call feature
There are many more things to Emerald including Johto Starters, Contests, Breeding & Ability Additions, Rare Legendary Pok�mon, Pok�mon from other Regions and many many more