There is a tendency among American millennials to be entranced by the French and Russian revolutions as a solution to our problems today. Let's look at how those worked by using historical data.
France
Well, the French revolution culminated with the House of Bonaparte being the Emperor of France, followed by a return of the Capetian dynasty, then a brief republic followed by the House of Bonaparte again from 1852-1870. If we argue that the First Republic was democratic, which is a stretch, it was unstable and didn't last more than a decade. The Committee of Public Safety had near dictatorial power and their democratic constitution was never even put into effect. The Reign of Terror killed over 40,000 people, most of whom were peasants. The Directory was highly corrupt and collapsed after only 4 years into another dictatorship.
After Napoleon became Emperor, the Capetian dynasty returned and ruled until 1848.
The 1848 revolution brought on the French Second Republic. It lasted only 4 years before Napoleon III became emperor. He fell after the Franco-Prussian war of 1870 and the Fourth Republic was proclaimed.
So what really gave France a stable democratic system was not a revolution but losing the Franco-Prussian War of 1870 when Napoleon III was taken prisoner in September 1870. A Republic was proclaimed 3 days later and it lasted until Hitler invaded France in 1940.
France as we can see became a stable republic not from revolution but because the emperor was kidnapped by the Germans.
Germany
Germany became a democracy first with the Weimar Republic, which was crushed by economic disaster as a result of the repayments after the First World War. West Germany became a democracy in 1949, and East Germany merged into the existing West Germany to form Germany in 1990.
This was not a result of revolution.
Russia and Eastern Europe
Mexico
The first Mexican Republic was plagued by coups and overthrown by the Centralist Republic in 1835. The Centralist Republic only lasted 11 years, before the Second Federal Republic was founded. Most of the presidents in this period lasted less than a year.
The Second Mexican Empire concluded with Emperor Maximilian I.
The Republic was restored for 9 years before the Profiriato took control in 1876 in a coup.
The Profiriato was overthrown by a revolution which lasted from 1911 to 1928. The current constitution of Mexico was drafted in 1917.
The Modern Mexican state was formed after the 1934 general election. There has not been a coup since. This can be seen as the start of Mexican democracy.
The Mexican Revolution of 1911-1928 arguably was a successful revolution which overthrew a dictator and established a democracy. That being said, Mexico still lags on most indicators regarding corruption and quality of life.
Uruguay
Spain
Spain has a very similar history to France, just delayed from their timeline. Their Sexenio Democratico started in 1868 and lasted only 6 years. The First Spanish Republic lasted only a year before the restoration of the Bourbons.
The Second Spanish Republic lasted 5 years before the Civil War and the rise of Franco.
Franco died in 1975 and there was a peaceful transition to a constitutional monarchy which remains to this day.
India
India became a republic after the Indian Independence Act of 1947 granted them independence. This came following 2 decades of civil disobedience under Gandhi's leadership. There was no violent revolution. India has had a stable democracy ever since. There are many issues India still struggles with today, regarding corruption and quality of life, but they are the world's largest democracy.
United States
The United States is one of the only countries in the world which established a stable system of government following our revolution, and we have never suffered a coup. We have been on our second constitution since 1789. We had a civil war in the 1860s over the issue of slavery, but no president has ever been overthrown in a coup and our electoral system has worked as it has been designed ever since. We have a flawed election system for president, and I believe it needs reform, but it has been stable, and it works.
China
The Republic of China had a successful revolution against the emperor in 1911. The Republic of China still exists today, despite the formation of the People's Republic of China in 1949. China is the only example I have of a country transitioning from a dictatorship to democracy, but not as a war of independence.
Iceland and the rest of Scandinavia
Iceland has the oldest parliament in the world. The Althing was disbanded for part of the 1800s when it was ruled by Denmark. They saw a gradual increase in autonomy until 1940 when Denmark was occupied by the Nazis and they assumed independence. Their isolation gave birth to democracy.
No country in Scandinavia gained democracy through independence. The closest you get is the independence of Finland, but this is more of a response to the Russian Revolution and opting out of being part of the Soviet Union, which the Soviets somehow accepted temporarily until they invaded Finland in 1939. Basically, no country in Scandinavia became democratic through violent revolution.
Italy
Following the end of World War II Italy had a referendum on whether they wanted to become a democracy. As part of their peace treaties Italy became a democracy.
Ireland
Portugal
Greece
Greece had a war of independence against the Ottoman Empire between 1821 and 1829. It was replaced with an absolute monarchy in 1832 which evolved into a constitutional monarchy in 1844. The Second Hellenic Republic was formed in 1924. In 1935 the House of Glucksburg returned to the throne until they were deposed in 1973 by a junta. The Third Hellenic Republic was formed via referendum and the Third Hellenic Republic was formed in 1974. The evolution from constitutional monarchy to democracy gave us the modern Greek state.
Conclusion
If we look at the history of other more recent democratizations in South America, we find none of which started their current form as the result of a revolution. There are also no examples in Africa or Asia either.
It is hard to point to any democracy except the United States clearly and see that their current form of government was formed from revolution. No modern social safety net started as a result of violent revolution.
All democracies have grown out of gradual change. Occasionally revolutions occur, but they have never been immediately replaced with a utopia.
The closest examples we have of successful revolutions which built lasting democratic institutions are the following:
- Independence
- United States
- Ireland
- Uruguay
- Revolution
- Republic of China
Those are the only examples I have. The issues with both of these countries in their post-revolutionary eras are obvious. But, despite their many issues, they have reformed significantly and today rank highly on most indicators.
The Republic of China is the only democracy which was founded as a revolution against another regime and has remained in power to this day over part of its original territory.