That's an interesting observation. Of course it need not be said that sales aren't everything. Metal Gear Solid 2 sold much better than Metal Gear Solid 3 but ask ten people which was a better game and 11 of them will tell you Snake Eater was better.

The funny thing here is that all I heard when XIII-2 was released was praise for how it fixed all the problems of XIII yet sales dropped off even more. It's perplexing.