General Augusto Pinochet became the dictator of Chile in 1973 in a bloody coup. In 1988, he tried to get elected for another eight years, but lost a referendum. In 1989 a peaceful election picked a new president of Chile and Pinochet stepped down, without incident, in 1990. Pinochet remained the commander of the Chilean army and was a Senator for Life in the Chilean legislature.

No

Samuel Huntington's democratization theory examines this phenomenon. In the 1970s, perhaps three quarters of the world's countries were governed by dictators, by the 1990s, the ratio has being reversed, with three quarters democratic to some extent. In the intermittent period the majority of the world's dictatorships fell.

The vast majority of dictators in the second half of the 20th century fell because of of the following factors:

1. decrease of legitimacy of authoritarian regimes due to increased popular expectation of periodic and competitive election, and/or poor economic performance or military failure.

2. Growth in global economic output helped modernize many less developed economies. Economic modernization, which includes structural changes like increased rates of urbanization, education, and a rising middle class, unleashes a constellation of social forces with the organizational capacity and education to press for democratic governance.

3. Changes in the Catholic Church brought about by Vatican II emphasized individual rights and opposition to authoritarian rule. This shift in world view was especially important for the Catholic countries of the Mediterranean and Latin America, as well as the Philippines, Poland and Hungary.

4. Regional Contingency Factor, also known as demonstration/snowball effects, happens when success of democracy in one country causes other countries to democratize.

5. External factors, most notably the efforts to spread democracy by the European Union and the United States.

And the examples of this are very very numerous. A wave of democratization in the 70s-80s started on the Iberian peninsular: Franco's Spain after his death and Portugal after the death of Salazar. It then spread to Latin America, where military governments in Chile, Argentina, Brazil etc were all replaced by civilian rule. This trend then spread to East Asia, where dictatorships in South Korea, the Philippines etc all fell. At the close of the 80s the left wing dictatorships in Eastern Europe and the Soviet Union fell as well.

In most of those cases the cause of transition to democracy and civilian rule was not so much because of armed insurrection, but because of the fact that the autocratic political elite realized that their rule was growing untenable, and that a voluntary exit was a preferred alternative that would allow them to keep some wealth/power/influence than fighting to stay in power.

The revolutions of 1989 in Eastern Europe were by and large non-violent, Romaina being the exception.

There's been a few good answers already that address the basic point but it's worth dipping our toes into the shallow end of statistics.

The empirical work on this question has been done by Milan Slovik in his Politics of Authoritarian Rule. It's an interesting work that avoids much of the categorisation of other studies of dictatorships, preferring instead some detail on theoretical models as to their behaviour. Nonetheless, for the purpose of this question, Slovik brings a number of empirical observations to the table.

The most relevant here of Slovik's findings (which are supported by others, eg Frantz, Tying the Dictator's Hands) is that the data supports the notion that very few individual dictators are deposed in mass uprisings or civil wars. To present the statistics:

Non-Constitutional Exits from Office, 1946-2008*

While this doesn't explicitly spell out the number of civil wars that accompany regime change in dictatorships, it should be clear that the threat to a dictator is likely to come from within the ruling elite. (There are a number of factors that affect this, including the existence of institutional bonds, existence of a party body and the relative strength of the military.)

So mass upheaval, a la Lenin, is very much the exception rather than the rule.

*Non-constitutional exists refers to circumstances in which a dictator was forced from office against their will. So Khrushchev was expelled from office by his peers, whereas F Castro voluntarily resigned in an arranged transfer of power.

General Franco of Spain seized power in a civil war during the 1930s but reinstated the monarchy and democracy after his death in 1975.