I think it's worth mentioning the obvious. XIII-2 has had more marketing than XIII which itself had marketing campaign budget unheard of in SE's history of FF titles.

I think this helps to clear up what can be seen from the sales of these 2 games. I honestly wonder though if SE sees it at all as they we're pretty frank about the fact that they don't want to do regular towns and exploration in FF games anymore:

"The game’s linearity was just because depicting towns and so on like we did before was impossible to do on an “HD” console – it was too much work."

Guess what there will only ever be HD consoles in the future.