It’s too soon to say.
The Cold War
If you just focus on Europe, the good guys won. The western European states were freer and more prosperous than their Communist counterparts, and the fall of the Iron Curtain in 1989 was a magnificent blossoming of liberty. When you look at the proxy wars they fought in the middle decades of the 20th century, however, both sides were about equally immoral and bloody-handed. And since many of those wars were bound up with rolling back the colonial empires that European powers had accumulated in the preceding three centuries, the west probably ended up on the wrong side of history here more times than not.
World War Two
Like the Cold War, if you focus solely on Europe, the good guys clearly won. Likewise if you focus on Japan and the places Japan colonized. If you focus on the places that everybody other than Japan colonized, it’s more of a wash. And remember that for the purposes of this discussion, Joseph Stalin was a good guy.
The American Revolution
Constitutional democracy: +1. Hereditary monarchy: -1. Non-white residents of North America: 0.
The American Revolution Versus the French Revolution
These are essentially the same revolution, except that the American one started thirteen years earlier and wasn’t a dismal failure that ended in Jacobin terror, Napoleonic autocracy, and the eventual restoration of the monarchy. In fairness, though, we had it easier.
Liberal Protestant 19th Century American Women
Abolition and suffrage: hooray! Temperance: boo! Just because you’re right about some things doesn’t mean you’ll be right about everything.
The right won the economic debate. The left won everything else. Let’s call it a draw.
The Vietnam War
North Vietnam won.
Europe for the Past 300 Years
Excellent job on the spread of reason, liberalism, and prosperity, and the creation of a viable alternative to religious/hereditary systems of government. Particular kudos over the past 150 or so years for the growth of feminism, which–to a first order of approximation–is the only social movement that matters. Shame, shame, and more shame for the spread of empire by force of arms and the animalistic delusions of racial superiority that abetted it. Open questions: 1) would the former have been possible without the latter, and 2) would things have turned out differently if another region had been in the driver’s seat?
China for the Past 300 Years
To be honest, it’s been kind of rough. But not to worry everybody: they’re back.
The 20th Century
Fascism, Communism, religious fundamentalism. Two down, one to go.