Well I think it took 9 weeks actually for Grand Theft Auto: San Andreas. Check out the comparison:
http://vgchartz.com/swlaunch.php?reg1=All&game1=New+Super+Mario+Bros.+Wii+-+Wii[35076]®2=All&game2=Grand+Theft+Auto%3A+San+Andreas+-+PS2[3427]®3=All&game3=Call+of+Duty%3A+Modern+Warfare+2+-+X360[28848]&weeks=15
Also it's worth noting San Andreas hadn't had a Japan release then, but if you align Japan launch with the others it still took 9 weeks.
So when we are looking at New Super Mario Bros Wii we could either do it consecutively or align all the weeks together from all regions (because Japan launched 2 weeks later) and go from there. Still looks like it should do it either way and definitely if align Japan launch with the others.