Ahem, the question is way too difficult to limit to just one performer. If I could give a top five (in no particular order) :
Obsession - Great looking and knew how to throw-down with no holes barred. She also knew how to be cool, yet hot at the same damn time.
Nina DePonca - Great looking and knew how to throw-down with no holes barred. Nina was my first real porn crush.
Julia Channel - Great looking and knew how to throw-down with no holes barred. She also had one of the best butts in the biz.
Ayanna Angel - Great looking and knows how to throw-down with no holes barred. She is too sexy for words.
Lana Sands - A real cutie with a nice round booty, and she also was known to share it from time to time.
I guess if you pressed me on which one of these were "the greatest", I'd have to say my girl Obsession. In addition to what I stated above, she has the volume of work, and consistency of hot performances that I believe might merit such a lofty title.