In the US, I don't consider Wii Sports a valid argument at all. It's bundled. Wii Play, I'm rather iffy on, because when you buy Wii Play, your not actually buying software. Your buying a bundle pack with basically a free (or near free) game with a Wiimote.
Japan? Totally different story. Wii Sports costs money, and is doing very very well. Had Wii Sports not of packed in the US, I would gladly consider it a normal, purchasable game, despite the lower pricetag, but it gives Wii software sales a brutal, unnatural advantage versus PS3 and X360 software (I feel), in the US. The top 2 selling games for the Wii in the US are either free, or actually counted as hardware since you pay $40 USD for a $30 controller and a $10 game. Is that fair? That'd be like counting Hexic HD as a normal software sale. Im not saying don't count it, but when we're discussing US software sales, it needs left out.
Attach rates for US/Japan:
In Japan, the attach rate for the Wii is 2.32 software units per Wii - Okay, but not quite what I think would be considered dominant. Again, this is due to budget titles in Wii Sports/Play moving about 45% of the software in Japan.
PS attach ratios are indeed abysmal - 1.5 units per PS3. Quite a bit worse than the Wii, because atleast there was atleast a decent bit of revenue for Wii Sports (around 4,000 yen x 1.8m units) and Wii Play (4,000 yen for controller + game x 1.2m units). But the tier ratios have improved much quicker for the PS3.
By the end of December, the Wii had an attach ratio of 2.09, and the PS3, a ratio of 0.99. Since then, the Wii's attach ratio has increased 10%, whereas the PS3 has increased 50%.
For comparison, the Xbox 360 had an attach ratio of 1.68, and by July of last year, had a ratio of 2.57 - an increase of 45%.
And again, the PS2, atleast as far as this website is considered (I think the sales are actually quite low, as the LTD attach ratio VGC has for PS2 is 6.0, when it was actually 10.0); was 1.33 by its first month, and was 1.69 by a similar period, but was without a holiday (like the Wii, X360, and PS3 had @ start). But again, I think the VGC numbers are most likely off by 50%.
If the Wii is to be dominant in Japan, the ratios need to improve faster than what they have. Although the tier ratios are "bad" (considering the lack of sales of actual fullprice titles), I'm not trying to be negative about it. The Wii attach ratios are certainly going to improve since DQS seems to be doing real well, and is full price. Again, I just think if the Wii wants to mimic PS2-type sales, it needs a strong tier ratio of atleast 3.5 or 4.0 by December in Japan.
Likewise, in the US, I have the data for the yearly, and attach ratios LTD, because I saved them all to my HDD before NPD closed the data down. The Wii has around a 4.3 attach ratio including 1.0 from Wii Sports, and about 0.3~0.4 from Wii play. The ratio is FAR better in the US, which it seems to have a decent ratio, but again, when compared to the PS3 and X360, it's not too great. The PS3 started out at 1.0 by the end of December, and is now at 3.0. The X360 started it's life out at 3.9, similar to the Wii w/ Sports & Play, but in the same timeframe, was at 5.0, and is now near 6.0 LTD. Whereas the Wii started out with 3.9, and has only increased to 4.3. So basically, the only thing that increased the actual attach ratio was Wii Play outside of normal full-price titles.
So basically, my synopsis is that the Wii attach ratios are not very good in either country, not entirely because of the actual ratio, but lack of increase despite games coming out. The US ratio is acceptable, but hasn't really increased in 9 months. Thats a huge problem. What happens when December comes around? Will consumers stay @ 4.0, and only buy a few games, while the PS3 attach ratio keeps increasing, and hits 4.5 or higher for actual full-priced games, and the X360 hits 6.5, or even 7.0 at the end of this year? With scenarios like that, it makes me question the ability for the Wii to dominate this generation - even if hardware does gangbusters, 3rd parties will realize consumers don't want the software like the fanbase of the PS3/X360.
This is nothing against Nintendo, but it's audience certainly isn't interested in much. Even for comparison, the NDS ratios are much better, as it enjoys a 5.0 tier ratio, and that is very strong for a handheld. So even despite the "casual" audience of the DS, and strong female demographic, the sales have still be awesome.