I have always found that there is unanimity in establishing that Beethoven has been the most important composer of all time. In the words of the Encyclopædia Britannica, for example, "The German composer and pianist Ludwig van Beethoven is widely regarded as the greatest composer who ever lived".
Although it is indisputable that this genius is at the top of the ranking, it has never been entirely clear to me why this first place is understood to belong to him. (In fact, I have always been surprised that Bach is not in the first position).
With regard to his role as the creator of the basis of harmony, it seems that Bach would be ahead of Beethoven; in fact, Beethoven himself called him 'the original father of harmony'. As for his role in the transition to Romanticism, it is often said that he did it together with Schubert. Nor was Beethoven the first in terms of the number of compositions (it is Georg Philipp Telemann who is credited by the Guinness Book of World Records as the most prolific, having written over 3,000 compositions).
So what is it that generates such unanimity among experts when it comes to classifying Beethoven as the greatest composer of all time?