But Bulbasaur is grass / poison type. Electric is not very effective against grass, so Bulbasaur will have an advantage unless Pikachu avoids using its electric attacks.
Edit: According to http://pokemondb.net/type , when Grass is attacking Electric, the attack is "normal," 100% of the damage takes. However, when Electric is attacking Grass, the attack is "not very effective," and only 50% of the damage takes.
So Bulbasaur is totally going to win this.