Pikachu cuz I made my 3 year old watch the indigo series. I also have a ton of his promos in a glass display case. Though I think she might of liked Ponyta just cuz she kept saying horsey
My daughter (6) loves Espeon, so much that she wishes she was one. My son’s (8) favorite Pokémon is Decidueye. Given my son and daughter probably know more about Pokémon than I do. Unlike myself, they actually play the games and are up-to-date with everything from the cards, games and show.
I’m still stuck on the 1st gen so my (26) favorite is still Mewtwo…
A 9 year old I babysit for really likes Torchic (and I had a hell of a time finding her a plush for Christmas a few years ago that wasn’t hideous or expensive)