Pikachu also has more than 4 attacks: Thundershock, Thunderbolt, Thunder, Quick Attack, Iron Tail and Thunder Wave (not exactly sure about that, but I don't know what other attack Pikachu used against Lt. Surge's Raichu at the end of the battle)
Personally, I think it's great if a Pokemon has more than 4 moves in the anime. Battles would be more entertaining then