First,it should be mentioned that there are some things that have changed, and that some things have not changed.the things that have stayed include:

• 8 Kanto Gyms
  
• 3 starter Pokemon(Charmander,Squirtle,Bulbasaur)
  
• Elite Four(Lorelei,Bruno,Agatha,Lance)
  
• Johto Victory Road
  
• RS TM/HMs
  
• Tag Team Battles
  

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And then,there are some things that have changed,or have been added.they are:

• Sevii/Rainbow Islands
  
• Johto Pokemon
  
• NationalDex
  
• Trainer Tower
  
• Deoxys
  
• Wireless Communications
  
• VS Seeker
  
• Fame Checker
  
• Union Room
  
• Compatability with Ruby and Sapphire and Colosseum
  

What's more,you ask?Just play the game to find out!