Pokemon had relatively little cut out and is probably 4Kids's overall best work. Not to mention it had the popularity of the games, cards and the rest of the phenomenon to help it along, it was DEFINITELY not an anime-only thing.
As for Yu-Gi-Oh, kids wanted a card game based off a cartoon about a card game. Plain and simple.
So yes, it is 4Kids. Especially considering their hackjob of One Piece was even worse than their Yu-Gi-Oh butchering