Whatever works. Let's look at the general possibilities: Autocracy, Oligarchy, Democracy...rule of One, Few, or Many. Communism, Capitalism, and Socialism are economic terms, not government. Representative Democracy is what the U.S. Constitution outlines for our nation, though we are arguably a Plutocracy in practice (oligarchy with the few being the wealthy).
But nevermind that. What works best is what works. An absolute monarchy (autocracy) could be peachy if that monarch is very benevolent. Democracy can fail miserably if the under represented are persecuted to the point of revolt, or if various groups detest each other (kind of like in Iraq now). The quality of a government of any kind is a direct representation of the quality of the people that make up that government (in a democracy it is the quality of those in the majority). Yes, in general, more people involved means a fairer governing and turnover in elected officials means bad times are shorter, but the general notion that more people ruling is better really has more to do with the perceived nature of those who seek power, notably that they are not as likely to be decent folk. So statements about democracy being the best form of government are really just statements endorsing a statistical sampling of decency in human beings.