I like the greek style of democracy, through it took a long time to get stuff done.
The same democracy that ended the life of a great philosopher?
And I just realized that I am yet to make a post...
It depends on the situation the country is in, what you mean by best, and the history of that country. For example, a war against a far inferior power that uses guerrilla style warfare (Think Vietnam or Iraq), then a communist or deposit style government is the "best", as it not only doesn't need public support as other forms of government are, but can control what the public can see meaning that they don't need to hold anything back. But of course this will have a huge effect on the countries economy, and would be nearly impossible to willfully apply the communist or dictator government in a country that has a history of despising those philosophies, like the United States of America, meaning that the current form of republic would work best for America for almost any situation do to the fact that it would be the only government that would be acceptable by the people under it.
Just to get more general, Democracies and Republics can work great for the welfare and happiness of the people living other them, but the people must be educated and reasonably wealthy, or the systems tend to be corrupted easily. The people also must have a way of making their vote, which would be difficult in a large poor nation. The public must not only be well educated, but well educated in current events, meaning that if the public doesn't have a strong support in the war, and it looks like they are losing, then they will probably surrender, especially if nearing an election. Though this does have the advantage of not being completely hated by any country, it is impossible to fairly do in any poor country.
The next general one would be Communism, as a government and as a economic system. This can work well in both poor and rich systems, though it can work better in arias where necessary items such as food, water, and fuel are scarce and must be rationed. As a government, it depends on a strong leader and/or leaders, which may be easier to find during formation but difficult to switch, if there is not a mechanism to replace him/her. This form of government can have a tight grip on it's people, meaning they have the advantage in warfare do to controlling what the people see and not needing their approval. It is impossible to place this form of government in a place like America that seems to hate Communism for some reason.
Well I assume that is enough for a start, correct?