I’ve been playing a lot of Pokémon soul silver recently, and have been wondering if I can still complete the national dex using only gen 4 games. I do not have an original model DS or a DS Lite, so I wouldn’t be able to migrate any Pokémon from gen 3. Is there any combination of games that I could play to complete the national dex?
Yes, you can. (Sort of/maybe). ThunderClapper is incorrect because you don’t need any mythical Pokémon to complete the Pokédex. However, you do need a friend or another copy of the game and another 3DS because of trade evolutions and to fill in some missing Pokémon in gen 3. (You do need Pokémon from R/S/E to complete the Pokédex, including the starters, legendaries, etc.)
No. You can’t complete the dex because you can’t get, Celebi, Shaymin, Manaphy, Jirachi, Deoxys, Mew, or Arceus. They are events and cannot be obtained in-game.