There is a phenomenon when an artist cannot create to the level of his earlier work or another artist's work. He is often compared to the earlier work and can't move beyond the achievement of this work. Is there a word (or a few words) to describe when this occurs?
Some examples could be:
Mike Nichols was never able to make another film that measured up to The Graduate. All works afterwards paled in comparison.
Italian literature has never been able to escape the specter of Dante's Divine Comedy; all authors have had to react to this magnum opus in their own way and reflect it -- or deny it wholeheartedly -- in their work.
Woody Allen's critics often refer to 'his earlier, funnier work'; in their minds, his later dramatic works don't always measure up.