DucksUnlimited on 03 January 2014
First of all, there have been plenty of doom threads about both so I don't know where you've been the past few weeks. And secondly, GT is very similar, if not more popular than 3D Mario games as a whole. Of course this isn't a 3D Mario in the traditional sense, but still.
Both have underperformed for reasons other than game quality so it's kind of silly to be upset about either game's sales TBH.
