I'm neutral on Pikachu, I don't hate it but I'm not a huge fan of it either. Despite this, I feel it does work as a mascot because it's both cool and cute as well as it being relatively easy to draw because of its simplicity.
I like the entirety of the Pikachu line. I especially love Raichu, but I've always felt it was the most under represented of the line. That being said I was pleasantly surprised to see it get some love when they came out with Alolan Raichu. The only thing that annoys me about Pikachu are the copies of it they make every new generation.
Pikachu as a Pokémon is OK. Not one of my favorite but I don't particularly dislike it either. It's cute and fun, and Pikachu as a character is cool too. I liked the story it got on season one of the anime and how it seems like he uses "Pika Pi" when referring to Ash.