GTA IV was a dissapointment to T2 in sales (I think), and therefore there was no backorder, because there was more stock than really needed. Therefore, this is only valid to compare how much it compares to expectations.
MGS 4 appears to outdo Konami's expentations, which is fairly incredible.
http://www.vgchartz.com/games/userreviewdisp.php?id=261
That is VGChartz LONGEST review. And it's NOT Cute Kitten DS