Well, 'The Greatest Show' is not rooted in reality. It's a purely imaginative work crafted for entertainment purposes. There's no factual basis behind it.
It depends on personal preferences. Some might consider it the greatest for its depth and influence, while others might have different favorites based on their own literary tastes.
Not necessarily. While Don Quixote is an important and influential novel, there are many other works that could also be argued as the greatest depending on one's criteria. It could be argued that different novels excel in different aspects, making it hard to single out one as the greatest overall.
It's hard to determine an exact length as it depends on various factors like the complexity of the plot and the way it's told. But some of the longest and most epic stories can span thousands of pages or hours of narration.