Holy crap! MGS is such a niche in Japan, it just beats the crap out of Super Mario Galaxy!
This could open about as well as Mario Kart Wii first week, if not better, leaving it as the 2nd best opener of the generation (on consoles) so far! Behind Super Smash Brothers Brawl only.
Not only that, after 1 week only, it could be in the top 8 of the generation!
http://www.vgchartz.com/games/userreviewdisp.php?id=261
That is VGChartz LONGEST review. And it's NOT Cute Kitten DS