EBD was not only the best Bally pin of 1981, it's the best Bally pin ever produced... PERIOD!
While it's true that 1981 was the best year for early SS Bally pins and represents the peak of the golden age of pinball, video games were a new novelty that definitely ate into pin sales.
There were several great titles from 1981 but all of them (including Fathom) took a back seat to Eight Ball Deluxe. I remember driving miles out of our way as teenagers just to go to an arcade or bowling alley that had Eight Ball Deluxe. No other pin could motivate use to do anything even close to that.