Although many have been tried and tested, I would have to say Democracy. It is not flawless, but it works fine for the world so far.
National socialism seems way too archaeic which is based upon the benefit of a single nation. Would it be effective for the Earth as a whole?
Socialsim. Every person must be helped by each other. Unfortuanetly all giving is not an adequate way of running the world or a country.
Dictatorship. I won't even go there.
Any thoughts and ideas on what you think is the best form of government and why? Could it be improved to become far more efficient?