If Ash wasn't a moron who worships Pikachu, would his favorite type be Flying?
I mean suppose he somehow had the opportunity to become a gym leader and he had to specialize in one type. Based on his team choices throughout all the generations, whoever offered him the job would assume he was a Flying-type ace, right?
He had every regional bird in his team at some point, and half of his his Kalos league team is Flying, but I don't recall him ever catching any Electric-types besides Pikachu
It seems like he has a preference whether he knows it or not.
Then again, by the time Ash grows up, gym leaders in the games will all have only one pokémon each, so it doesn't matter.