Oh, absolutely, but there are some that are far more contact-based than others. Ghost attacks shouldn't do as much damage to most Pokémon as they do at the moment, for me, and I could see a Ghost type being weak to fire, electric, psychic, dark, fairy... but seeing Haunter get destroyed by Earthquake has left me rather annoyed. xD

EDIT: I don't want it to null them, but at least be "not very effective". It just doesn't make sense for a rock thrown at a ghost to do regular damage. They lose their... ghost-ish-ness.