Part of the comparison between Wikipedia and other encyclopedias are the book shelve comparisons: How many volumes would a printed Wikipedia fill?
I made some clicks on the “Random article” button of Wikipedia in German, and then made a PDF of the articles. Then I estimated that one PDF page is the equivalent of two-thirds of a page of Brockhaus Enzyklopädie (the 30 volume edition of 2005/2006).
So I calculated that the 1,250,000 articles of Wikipedia in German could fill 675 Brockhaus volumes. This picture here tries to give an impression. Of course it were better if a skilled graphic artist took over the task and show a library with Wikipedias in different languages, as well other encyclopedias.