I’m not sure if you can recall what it was like before Wikipedia, but I can. I remember doing web searches for basic information on a subject and coming across a hopelessly-outdated, subscription-only Encyclopædia Britannica article. Now, up-to-date information that’s pretty accurate can be found for free on subjects far more comprehensive than any printed encyclopædia could ever hope to cover. Wikipedia is one of the best things the web has ever produced.
Update: Apparently, Portuguese Wikipedia users are particularly interested in paper sizes, and Chinese users in Tiananmen Square.