Tobold had a bet going that with the release of the Mists of Pandaria expansion, World of Warcraft would retake the top spot on The Nosy Gamer's rankings of the top twelve MMORPGs. Guild Wars 2 had held the top spot since its release last month.
Nosy Gamer's rankings are based on data from Xfire and and thus reflect its fairly hard core demographic, so with this week's rankings out showing WoW indeed beating GW2, Tobold gets to crow about being right.
But since games are now played by people far outside the narrow demographic of hard core gamers measured by Xfire, I'd like to call attention to another source of data which can be used to measure a game's popularity—Google Trends.
Below I'll show that the Google Trends dataset reveals WoW's long-term decline despite the four expansions released over the years. It also shows that while a few western MMOs have spiked above WoW's popularity for a short time, only one asian MMO has been able to sustain it. There are a few western games that are more popular than WoW but they're not MMOs.