So how popular is Diablo 3 really? Check out such trends from Google Trends, and compare with other games... Starcraft 2 and World of Warcraft.
It is clear picture when Diablo 3 got announced it was very popular, and it seems to be more popular than Starcraft 2, and there still little work to World of Warcraft ;-).
It is also interesting to check out contries, cities and regions where Diablo 3 is most popular.
Check out the Diablo 3 search trends