DING-DING-DING DING-DING

Oh, if anyone is debating who had the biggest tier ratio:

It wasn't the Wii. The X360 had a lead of 1.1 software units per console. And I do believe this chart includes all Wii games including Wii Sports, FYI.

The article is at:

http://www.pcworld.com/article/153419/software_attach_rates_for_xbox_360_ps3_wii_calculated.html/

Also, from PCvsConsole.com - a global list of attach rates:

NES
Japan - 11.764
America - 6.790
Other - 5.057
Total - 8.096

SNES
Japan - 11.359
America - 5.781
Other - 5.737
Total - 7.722

N64
Japan - 7.175
America - 6.886
Other - 6.394
Total - 6.834

Game Boy
Japan - 4.836
America - 4.326
Other - 3.636
Total - 4.221

GameCube (End of 2005)
Japan - 6.693
America - 9.838
Other - 8.550
Total - 8.945

Game Boy Advance (End of 2005)
Japan - 4.183
America - 4.728
Other - 3.603
Total - 4.300

Nintendo DS (End of 2005)
Japan - 3.246
America - 3.700
Other - 2.624
Total - 3.216

Xbox (Unofficial, End of 2004)
Asia - 4.706
America - 9.773
Europe - 8.200
Total - 8.945

PlayStation (End of June 2005)
Japan - 13.201
America - 9.122
Europe - 7.552
Total - 9.367

PlayStation 2 (End of 2005)
Japan - 8.454
America - 11.222
Europe - 9.294
Total - 9.885

PSP (End of 2005)
Japan - 1.857
America - 2.892
Europe - 1.892
Total - 2.269

So there you have it. The Playstation 2 has the highest attach rate after ~5 years on the market @ 9.8 units, but has increased to around 11-12 now.

Also, vgsales @ Wikia.com has the following ratios for systems @ 30 months:

http://vgsales.wikia.com/wiki/Software_tie_ratio