Come to think of it;
Pewter City is next to Viridian forest, filled with bug pokemon right?
Rock beats Bug
Cerulean City has a lot of caves surrounding it
Water beats Rock
Vermillion is a port city
Electric beats water.
Ahh nintendo logic.
Fuchsia City has a safari zone, filled with trees.
Poison beats Grass
Cinnabar Island is near to Seafoam Islands.
Fire beats Ice
crasher Wake is next to a marsh
Ground beats Water.
BTW, What do you mean by "Nintendo Logic"?