What's An Orator? Who's A Great One?

Last night, as guests at  neighbors for a delicious Shabbat Eve meal, I found myself in a friendly argument.

What is an orator?
Who can be considered a great one?

I think that we all defined the term orator differently, which was a contributory factor for our disagreeing.  It may be that I was the only one who insisted that a true top notch orator can speak convincingly without notes and certainly without a teleprompter.  The best IMHO can come up with a mesmerizing speech off the cuff, just answering a question.

As I see it, an excellent orator composes his/her speeches.  A top orator isn't a well-rehearsed actor reciting/reading the words of others.  But the dictionary only credits orators with delivery:

1: one who delivers an oration
2: one distinguished for skill and power as a public speaker

This Encyclopedia Brittanica definition of oratory supports me:

"...basis for the art of oratory, is the art of using words effectively..."

What do you think?  And who do you think fits your definition of a great orator?  And who isn't?