I dont understand people who get to a democracy as soon as they possibly can, skipping other forms if possible. The way i see it, it is a stupid idea to become a democracy if u have any less than 15 or so cities.
I always try and wait until I have grown beyond that barrier before become a democracy because at that stage you can become basically a "super" democracy where it is quite possible to conduct a successful and lengthy war against another power, without disorder with your luxury rates at only 20%.
I have only once abandoned Democracy once during a war, and that was in favour of Fundamentalism during a rather annoying war with a much bigger neighbour. And that was only because under fundamentalism u could churn out a lot of units very quickly to perform a "blitzkrieg" against the enemy, to achieve a peace treaty and then restablish Democracy, after disbanding all the un-needed units.
I have also noticed that if u are a larger empire and you are a democracy you tend to have a very high rate of production, so u dont even need to have a standing offensive army because you can quickly produce one in one or 2 turns...

The only time I have ever used Communism was when my empire covered a good portion of the world and it became extremly difficult to manage under democracy even at 40/50% luxuries, and even then I dropped it in favour of Fundamentalism because I kept loosing money. In my view there is no point in having good science if you cannot afford to build the things you research.
Basically my point here is that each Government type has its own merits, and more than likely u will use each one of them at some point for some reason, and there is really no better government because Despotism is the best government at the beginning of the game because your small and Despotism allows quick expansion, Monarchy is good early in the game if you need to conduct a war or have not yet discovered Republic, Republic is good if you are a medium sized empire and have not yet discovered Communism because communism is a good replacement for a medium empire that needs to conduct war, or if you havent discovered Democracy, Democracy is good because of its Science bonus and quick growth for your individual cities and that it is easy to support a large empire, and Fundamentalism is a good alternative for a larger empire which is at war.
(Damn that was hellava long winded LOL)