This is something I always wanted to comment. It's about two big mistakes since Generation 1 of Pokemon that it seems they are not willing to correct. It's around two of the most popular Pokemon of all: Gengar and Gyarados. You see:

1º) Why is Gyarados a Water/Flying type? First of all, he's not even capable of learning "Fly". Second, although it is one of most powerful Water Pokemon, it's too weak against Electric; even with its types. Mantine has the same types but it resist them better. Considering his appearance and lack of members for some Pokemon types in Gen I, Gyarados should have been a Water/Dragon type since Gen 1. So, why they haven't changed the big error of this Pokemon yet?

2º) Why is Gengar a Ghost/Poison type? First of all, Ghost Types were supposed to be the only weak point for Psychic types. Yet, with its Poison type, it became practically useless against Psychic attacks. Not to mention that Lick was the only true Ghost attack, which made Psychic types practically unbeatable. And second, being Poison Type and yet, it doesn't learn any Poison attack, outside of TM and HM. So, Gengar should have been a pure Ghost Type; or maybe a Ghost/Dark type Pokemon, to make it more tricky. So, why they didn't changed this big error too?

Some Pokemon suffered changed in types when Steel, Dark and Fairy types were introduced. So, why they didn't fix this too big mistakes in Pokemon history?