Those numbers are actually pretty terrible for the PS3 side of the house seeing as how Final fantasy is often viewed as a "Sony" game and how the 360 port wasn't handled with as much care as it should have beemGoing back to the original poll of who's playing the game on what;
http://www.digitalspy.co.uk/gaming/news/a208752/ps3-ffxiii-outsells-360-counterpart.html
Also, interested re a potential sequal;
http://www.digitalspy.co.uk/gaming/news/a208746/square-refuses-to-rule-out-ffxiii-sequel.html