Haha, I actually think the Pokémon Company’s Pikachu collection is smaller tbh, unless you combine all their locations. In Japan the Pokémon company has (close to) all Japanese Pikachus, as they’ve displayed them in a Pokémon Center once. I’m sure they also have all English Pikachus in a safe somewhere as well. Still, my collection might not be complete, but I have all languages at one place, so I’d argue my Pikachu collection is larger than that of the individual Pokémon companies around the world. 
Pretty insane when you think about it actually. 
As for who has a larger collection than me, that would be Tom, a collector from Belgium and online friend of mine. He also helped me quite a few times in the past with cards; I wish I could say the same towards him… he’s better in finding contacts around the world it seems. I did help him a few times, but not as much as vice-versa.
If we only look at official releases (so without errors, autographed cards, and such), he has about 25 more than me right now. Including those I’m not sure who has the larger collection. He has a lot of autographed cards. And errors I think we’ll have about an equal amount, give or take a few.
But whoever has the largest collection doesn’t really matter. We’re both going for a complete collection one day, and won’t stop anytime soon. Here is his recently started Instagram with some of his recent additions and highlights.
Greetz,
Quuador