I'm not sure whether the OP will revist this thread after insulting Mass Effect 2's sales. but Mass Effect 3 is nearly out and it will undoubtidly sell more copies than FF13-2. as Mass Effect 2 has sold more copies than FF13-2, yet being a timed 360 exclusive.
for a more fair comparasion The Elder Scrolls 5: Skyrim has sold 10 mil copies in a shorter time span than FF13 sold however many copies it sold in the first 3 months.