Ok everyone knows the whole argument about wii sports being bundled can skew software sales for the Wii high.  However, the game DOES affect attach rates because it is still a game that a lot of people want and a lot of people would play.  If they don't have this game, they will buy another one, thus you can't discount its effects on wii software attach rates.  

So the question is how to figure out what its sales would be if it wasn't bundled.  This will obviously be hypothetical but its an interesting exercise just to see what the effects might be.  

To figure it out, we'll use two point controls: Japan sales for Wii sports and both countries sales of Wii Play.  Now I know Wii Play isn't the best control to adjust but it targets a very similar demographic and is a very similar game aside from the wiimote bundle.

 So: 

LTD Wii Sports sales in Japan: 2,273,411

LTD Wii consoles in Japan: 3,951,437

LTD Wii sports Attach rate in Japan:  57%

 Now you can do a simple exact comparison vs US assuming same attach rates.  Since US LTD wii console sales are 7,031,085, if you assume the same attach rate, that'll mean Wii sports will have a likely 4,045,248 sales.  That's still really high and I think reasonable since everybody knows wii sports is still being touted as one of the main reasons people buy the Wii (the only reason according to some fanboys).

But now to test the assumption of whether the attach rate in Japan will be the same as the US.  Obviously it'll be very difficult to tell and I had a hard time figuring out a game that will target the same demographic as Wii Sports.  Obviously choosing the attach rate of a FPS in Japan and using that to estimate the attach rate of a FPS in US wouldn't work.  With that disclaimer, we'll operate off the assumption of using Wii Play. 

LTD Wii Play attach rate in Japan: 1,816,224 / 3,951,437 = 46%

LTD Wii Play attach rate in US: 3,149,774 / 7,031,085 = 45%

Interestingly, this implies that the demographic market/sales for Japan and US is very similar for Wii Play and assuming that its the same demographic for Wii Sports, then we can say that US would have similar attach rates for Wii Sports as Japan.

This is a slight difference in attach rate, will Japan having a miniscule % higher, so if we adjust that, it'll come out to Wii Sports having an attach rate in US of around 55.7% which ends up at 3,920,679 still really high. 

My opinion is that this more likely represents the sales of wii sports if it wasn't bundled.

And if you have an opinion of another game other than wii play to extrapolate attach rate, go for it.  I picked it cause it made the most sense to me. 

Depends how much it cost; if it was $20, then an 80% attach rate; if $30, then 70%; $40, 60%, $50, 50%

This is assuming Wii sells that much without as many people demonstrating Wii sports, eh?

If it were cheap then pretty high, arround 60%.