I think the beauty of Keith's stroke is his follow through. He takes a very short backstroke, but then pushes right through the cueball. Tommy Kennedy has similar stroke mechanics. I've tried to emulate that type of stroke, and when it works, it seems to make shooting effortless. All the effort goes into the "push through", almost like a dart player.
Another mechanically perfect stroke is George San Souci's. I was sitting with Hal Mix out at the Reno Open in the late 90's, and I asked him who had the best stroke. He said in his opinion is was San Souci's. I don't know if Ginky plays anymore, but he had a lovely stroke.
My all time favorite? "The Rifleman", Buddy Hall.
Doc