As research for my bestselling book on Public Speaking, I listened to dozens of famous speeches. I found a list of the top 100 speeches of all time and worked my way through it, making the following observations:

• We have technology bias.  Since we don’t have recordings of, for example, Lincoln’s Gettysburg Address, Jesus’ sermon on the mount, or Cicero at the Roman Senate, this top 100 list is really the top 100 audio recordings of speeches of all time. There are hundreds of years of great speeches that will never make this list, even if we extend it beyond the 20th century, simply because we’ve never heard them spoken.
• There is a difference between a great written speech and a great performance. No living person heard Lincoln actually give the Gettysburg address.  It’s debatable how good a speaker he was. Many of the speeches in this list are noteworthy for their content, but not necessarily for how they are presented (e.g. Faulkner’s Nobel Prize acceptance speech).
• None of these speeches used Powerpoint, or had media of any kind. It’s a reminder that it’s your ideas and how clear you can be in expressing them with your voice that matters more than anything. Some of these speeches were clearly read from a script, but many were developed through practice and using a system like the one I recommend.
• We have cultural biases that affect who is listed.  I have yet to find a proper international list of the speeches of all time. Most of the lists I’ve found are made in the U.S. and/or Google has a strong U.S. bias since that’s where I’m searching from. I also only understand English, so even if there were an international list, it would have to be translated. And of course, history biases which speeches and ideas will be honored:  Hitler and Mussolini were both notable public speakers, but I doubt we’ll see them on any lists like these, even if they belong up there.
•  Malcolm X is one of the best speakers on the list. I certainly don’t agree with all of his points, especially his more militant early work, but he succeeds at being natural, provocative, funny, intelligent and passionate in ways few on this list do (Try White Man’s Law as an early example and Any means necessary for later). MLK is far more theatrical in the way he presents, and I like it less (although he is exceptional). Many of the speeches in this top 100 list are by politicians, and are unsurprisingly stiff and rehearsed sounding. Even JFK comes off this way in some of his most famous speeches.

[Updated/edited: 1-13-16]