Well, you really can't get Chikorita,Cyndaquil,or Totodile in Pokemon Emerald until you complete all 202 pokemon of Hoenn. That doesn't include the GSC pokemon or Kanto pokemon. It just means plain Hoenn pokemon. All the Hoenn pokemon. All 202, including Deoxys, and Jirachi. It will be difficult, but its worth it. When you do catch the 202 pokemon of Hoenn, make sure you go talk to Professor Birch, because he will give you one of the three Johto Starters: Chikorita, a sprouting grass pokemon, Cyndaquil, a fire-mouse pokemon, or Totodile, a crocodile water pokemon.

Chikorita evolves into Bayleef, which evolves into Meganium. The best moves for Meganium would be Solarbeam,Giga Drain,Razor Leaf,Toxic

Cyndaquil evolves into Quilava, and then into Typhlosion. The best moves for Typhlosion would be Flame Wheel,Fire Blast,Fire Punch,Dynamicpunch

Totodile evolves into Croconaw, and later into Feraligatr. The best moves for Feraligatr would be Hydro Pump,Slash,Blizzard,Mega Punch

If you want these strong, rare pokemon, be sure to collect the Hoenn pokemon!