Extreme Pokémon: The Guide For The Ultimate Fan has a quiz where it pits two Pokémon against each other.
The answer for Golem vs Pikachu:
"Pikachu will win, because Water-Type Pokémon have the advantage over Rock-Types."
They have a point, though - Water types do beat Rock types :') Flawless logic.
Maybe it's a Surfing Pikachu?
Maybe they mean Pikablu.
Of course Pikachu will win. Hasn't the anime taught you anything? :P