Depends what you mean by "big thing" - it's sort of a subjective measure. The most recent fair The 2010 Shanghai World's Fair attracted 73 million people and 246 participating countries/international organizations (source), making it over twice the size (by those metrics) of the 1889 Paris Exposition Universelle (source) which was phenomenally successful for the time.

I think a big factor to them being perceived as "less of a thing" to our western perspective is that they used to be held quite frequently in the United States and Europe. Now that they're more evenly distributed we haven't had one in the US for over three decades. The last one we saw was the 1984 Louisiana World Exposition, which saw 7 million guests and the "Wonderwall" which was described as a half-mile long stationary mardi gras parade.

It's also worth noting that "World's Fair" also used to be commonly used to describe a lot of much smaller events, such as the 1936 Andra Internationella Luftfartsutställningen I Stockholm, which was essentially a grand opening for an airport. In more recent times the term hasn't been commonly used to describe anything other than very large events, potentially inviting the impression that there used to be a very large number of these very large events.

The trade show aspect (incredible new steam engines! super-sized canteloupes!) was supplanted by industry-specific expositions.

The aspect of displaying unusual foreign cultures and faraway lands came to seem exploitative, and didn’t interest nations who wanted to demonstrate how modern they were, not how primitive or colorful. In addition, it became possible for large numbers of people to simply visit other countries instead of viewing a reconstructed village.

The midways full of thrill rides were supplanted by theme parks such as Disney and Six Flags.

Television reduced the curiosity-seeking value of static displays, and pavilions began to simply be theaters for viewing television programs.

Late-20th century expos, especially in North America, seemed overwhelmed by the corporate pavilions, which were of dubious marketing value to the companies and seemed a little distasteful to attendees.

Morris Dickstein expands on these themes in his essay “From the Thirties to the Sixties: The World’s Fair in its own Time,” published in Remembering the Future: The New York World’s Fair from 1939 to 1964.

hi, you'll find a few comments, and links to more posts, in this thread

• What ever happened to world's fairs, great expositions, etc.?