Just toooo many people, you have to queue many hours for each pavilion.
I highly recommend:
the Belgium pavilion's restaurant for its beers
the German pavilion's restaurant and bar for its beers
the Polish pavilion's restaurant and bar for its friendly staff and therefore free vodka
Some of my friends went to the Nepal pavilion there was a huge queue, but just at the entrance are no barriers, so they just got in right there. The guard saw them and gave them a "nicely done guys!" look!