While I agree with your analysis in general, I still believe that Cash was right in saying that Federer had a considerably weaker field during his prime years. However, your point about the duration of Federer's reign as compared to Novak's splendid one year run cannot be disputed. Thanks for a balanced post.
Thanks teacherling. Federer, indeed, did not have competition like Djokovic has currently, I agree. Because let's face it, usually, it is tough being the number one player in the world, and having players at number 2 and 3 respectively, who have won in total 25 slam titles between them.
That doesn't happen everyday.