This is awesome Sky Render! You are a hero! Here's some crap I just cooked up with this amazing spreadsheet and VGC's worldwide weekly software sales charts.
Lowest and highest weeks for hardware sales in 2008:
Wii lowest: 37.88% (12-Jan)
(Wii had supply problems after Christmas, and no new games on any system were in the top 30)
Wii highest: 67.48% (24-May)
(Haze week, lulz!; a random insane supply rebound a few weeks after MK Wii/GTA4 week)
360 lowest: 14.87% (28-Jun)
(3rd MGS4 week, and insane Wii gains)
360 highest: 30.44% (4-Oct)
(FIFA 09 week)
PS3 lowest: 15.05% (20-Dec)
(I guess it's too expensive for post-economic-collapse Christmas? Only 1 PS3 game in top 20 this week)
PS3 highest: 42.66% (14-Jun)
(MGS4 week)
The 360's best week for marketshare wasn't as good as the Wii's lowest week.
The PS3 beat Wii's lowest week of 37.88% just once, in its 42.66% week, the one week it outsold the Wii, thanks to MGS4. That week Wii sold 42.29%, and it was the Wii's 2nd lowest week.
(PS3's 2nd best week was 35.16%, the week of January 12th, right behind Wii's lowest week at 37.88%. So the PS3's best 2 weeks and the Wii's worst 2 weeks were the same 2 weeks.)
This makes it look like PS3 had a better year than the 360, but while the PS3 had a solid 2nd place during the earlier parts of the year, the 360 took 2nd place for the more important part of the year. The 360 took 2nd place the week of September 6th and never gave it back.
Wii had:
1 week between 30% and 40%
10 weeks between 40% and 50%
38 weeks between 50% and 60%
3 weeks between 60% and 70%
or
11 weeks under 50%
41 weeks above 50%