LP,
My point about Napoleon was that he was faced with the difficulty of the ruling elite of Europe wanting nothing less than him to be removed from power, and he was not the aggressive imperialist that he is portrayed as. And overall, his rule in the precious years of peace he had was prudent and beneficial to France.
Speaking of Spain, they really don't count. The Spanish Empire was effectively crippled long before representative government was broadly viable in Europe. They never invested their gold in anything meaningful like infrastructure, and so they never capitalized on the good foundation they built. The other empires that survived in to the 1900s, however, were more prudent with the resources they had at their disposal.
Secondly, with all the benefits of representative government regurgitated, the ability to remove an incompetent leader or for government accountability to the people, they don't seem to be actually true, for long anyway. Whether ancient or modern, representative governments are consistently dominated by private interests. There are periods of strong leadership, such as the presidency of Teddy Roosevelt, but usually the government is more concerned about the private interests they depend on than they are with the people. And over time, the representative government gets elitist to the point of the late Roman Republic, where an Emperor became an absolute necessity. And I dare say that America is getting to that point now.
An autocracy, while not necessarily true, can provide a long-term period of strong leadership. It is in the interest of the autocrat to nurture the state, because their power depends on how well the state is doing. It would be imprudent for an independent autocrat to cater to private interests that harm the state, because that would weaken their own power by channeling it to other individuals as well as weaken the state.
Yes, an autocrat's successor can be, and often is, a short sighted moron. However, an autocracy does not need to base succession on family. During the period of the Five Good Emperors, succession was decided on merit. Little wonder why those Five Emperors were so great aye?
A weak government is dependent on private interests, and when private interests are highly influential the state is weakened by their short-sighted greed. And the only way to have a consistently strong government is to have an autocrat, and perhaps we should learn from the Romans that these autocrats should be selected on merit.