I mean, Pikachu's definitely a good character, and I'm not trying to put down the dude's skill, but isn't it pretty much a meme at this point that ESAM habitually overrates the character? "Only loses to Olimar and sort-of-kind-of Ness" makes me suspicious -- I'd expect more people to pick him up if that were really the case.
I think a lot of the -1 matchups are probably even and Pikachu probably loses a few more matchups. I don’t know enough about Pikachu to have a deep comment on this but ESAM has always been quite biased. He’s a great player but his biggest flaw might be his bias