I spent some time noodling around looking at what games are really popular (I wouldn't know firsthand, I don't play much). There's some data at http://www.amazon.com/gp/bestsellers/videogames (click on PC Games). I tried to cross-check titles with Google Trends to see which ones seem enduringly popular, but I haven't found any that beat World of Warcraft yet: http://www.google.com/trends?q=world+of+warcraft%2C+guild+wars%2C+tomb+raide...
Is Google search popularity a bad measure, or does it reflect the public's mood well? - Dan