I think it sells well because it is so different. On on side, it's like a good movie you want to see more than just once. On the other hand it's still interactive and you can change everything in that movie.
My father was never much interested in Gaming but when I showed him heavy Rain he was totally thrilled.
PS:
Heavy Rain Metacritic > Final Fantasy XIII Metacritic.
'nuff said.
updated: 14.01.2012
playing right now: Xenoblade Chronicles
Hype-o-meter, from least to most hyped: the Last Story, Twisted Metal, Mass Effect 3, Final Fantasy XIII-2, Final Fantasy Versus XIII, Playstation ViTA
bet with Mordred11 that Rage will look better on Xbox 360.