First of all, check your subtraction for the past 52 weeks.
Ignoring the 3 weeks after MGSIV was released then you must also remove the 3 weeks that the 360 did best - that's only fair.
And even then, i don't think you maths is valid. Historically the 3rd year is the year in which a console has the highest sales - so in 2009 360 sales should drop and PS3 sales should rise







