Well as I said earlier 360 really is a curious case. It has nothing to do with the owners or userbase stereotypes. It is a second place console (noticeably) getting big brands and high profile games. Compare that to the original Xbox and/or Gamecube last generation. Both of those (aside from 1st party) weren't getting any of those. And if they were, the majority of sales would go the PS2 version as it was the "main version".
Not the case for the 360 compared to the Wii. It is getting most of the high profile and big branded games. Even if the Wii is getting them as well the 360 version is seen as the "main version". Now mix that with sales unfitting of a first place competitor and you get big software sales compared to smaller hardware sales. Nothing really that MS did but there are few reasons why. One, it came out first and got huge developer support. Second, it wasn't a huge transition from the way gaming used to be. Developers could adapt easy and flawlessly to bring their "old games" to the "newer versions". Finally, it's not as difficult and expensive to develop for compared to the PS3... if you were wondering why the PS3 didn't get that position.
So it is essentially gaining this high attach ration becuase of the reason for the big software and the reasons for the lower hardware sales. That doesn't mean it is selling more software than the Wii (which is apparent) but Wii is selling more hardware compared to that driving it's attach ratio down or not growing as fast. So I guess it is kinda the luck of the draw that the 360 is achieving this considering it has nothing to do with the console whatsoever. Or maybe it's just because Wii is such a radical change for development and DIDN'T come out first. Either way 360 is going to have some record attach rates because.
