I look at it like this...

As far as meaningful and deep content goes, Woltz's monolgue did not have any...He did not say anything profound, its more about WHAT he said and HOW he said it accompanied with his facial and body mannerisms....It was very well acted...It was more along the lines of one of those memorable movie scenes that stands out considering following that speech of his was perhaps one of the most famous movie scenes of all time...That monologue was in its own right, very defining of what kind of man Jack Woltz was and the way he sort of takes out his disdain for Fontaine on Hagen was evident...I can't argue that this was the greatest monologue because it is open for speculation...I am stating why I think it was a great one...Wether or not it was the greatest, I don't think it can be argued that it was the most emphatic monologue in The Godfather...