You must not follow sales much. Weekly game sales typically look like an exponential decay. Mariokart Wii has been out for a while, so comparing its week 10 sales to MGS4's week 1 sales is silly. MKW sold 580K its first week in Japan.
I am sorry, I think you misunderstood the reason for the inclusion of Mario Kart and Wii fit's sales. Let me explain.
To get to my point, answer a couple of questions:
1) Do you think an increase of 7 times the number of systems in one week was a fluke caused by some random sale or can we attribute it to MGS4?
2) If we can attribute it to MGS4, is it safe to say that MGS4 is selling consoles?
I know it will drop off, and am not claiming it is the herald of a new era of supreme dominance for Sony or anything of the sort. I was indicating that MGS4 is selling systems. As a matter of fact, this one game pushed mid-June sales into the holiday sales range - even if for only a couple of weeks. It is a good example of a game that sells consoles.
Now, I included the number 2 and number 3 software titles so you could compare how MGS did against other titles selling in this week. As I am sure you know, there is a large seasonal dependence on software sales, so you cannot compare week to week. Because of that, I was trying to give context for an individual week's worth of sales. I assume most people here already know about the software drop off and would realize that I chose the number 2 and 3 software titles - NOT that I picked titles on the Wii to try and do some sort of cross console or cross weekly comparison. They were to give context to the overall size of the game market this week in Japan for this week.
If I had done the same thing during Mario Kart's release, I would have chosen Monster Hunter Freedom for the PSP and Mosou Orochi Maou Sairin for the PS2 as context numbers. At the time, I am fairly certain most people would recognize those games as being in their 3rd and 2nd week respectively. So it does indicate that Mario Kart Wii was selling very well, commanding an impressive chunk of weekly sales all to itself even with stiff competition. For this week, Mario Kart and Wii Fit have been out for a while, meaning that MGS4 did not face stiff competition from new releases (although there were a couple of new titles in the last several weeks). This indicates that MGS4 got a lion's share of software sales for the week. At the same time, weekly software sales around that time hovered between about 1.5 million and 2 million, where at this point in the year they hover around 800k to 1 million. As these numbers fluctuate wildly, showing what titles are 2 and 3 and how much they sold indicates more about the overall market that week. That is why they were included.
I wanted to keep my post brief so tried to provide only context numbers that those who followed sales could interpret themselves. It was not an attack on the two games I mentioned or onto the other systems. At question here is whether or not a game can sell systems - not which system is selling more.