This isn't saying the Geneva Bible's best, it's saying it's preferred by readers.
Shouldn't 'best' hinge more on accuracy of translation and inclusion of relevant texts -- or is the Bible's prime function pure propaganda?
A technical article in Nature might have a hundred times the information of an article on the same thing in The Sun or National Enquirer. Which one is 'better'?
"Preferred because of it's sheer power of excellence", which means it is great in every way...it is excellent. And it came over here on the Mayflower which is kind of nifty.