About half of the Pokemon you can find keep their Japanese voices. I believe they are Charizard, Metapod, Butterfree, Kakuna, Pidgey, Pikachu, Zubat, Diglett, Dugtrio, Psyduck, Mankey, Growlithe, Arcanine, Victreebel, Graveler, Rapidash, Magnemite, Magneton, Doduo, Shellder, Cloyster, Staryu, Electabuzz, Magikarp, Gyarados, Eevee?, Porygon, Dratini, and Dragonite. I think Vulpix keeps its Japanese voice, too, but I'm not sure if it says "Ro" as in its original name "Rokon", or if it says "Vul".
About half of the Pokemon you can find keep their Japanese voices. I believe they are Charizard, Metapod, Butterfree, Kakuna, Pidgey, Pikachu, Zubat, Diglett, Dugtrio, Psyduck, Mankey, Growlithe, Arcanine, Victreebel, Graveler, Rapidash, Magnemite, Magneton, Doduo, Shellder, Cloyster, Staryu, Electabuzz, Magikarp, Gyarados, Eevee?, Porygon, Dratini, and Dragonite. I think Vulpix keeps its Japanese voice, too, but I'm not sure if it says "Ro" as in its original name "Rokon", or if it says "Vul".