I think it's rather sad that not only does the Wii's glorified last-gen hardware screw it out of third party retail games but the size-restriction and lack of a hard drive causes it to lose out on downloadable games as well. Seriously it is like everything about the Wii is restrictive in some way that would turn off other developers.
Ignoring the sales of the machine, what aspect of the Wii from a hardware perspective would entice a developer to work on it? It is pretty much the worst in every category. Motion control was the only ace in the pocket and that isn't a unique feature anymore. The Wii is where Nintendo's approach of designing hardware solely for their own needs caught up with them, where even selling the most consoles doesn't attract support. The machine itself is so unappealing and inadequate that developers will stick with systems that have like half the userbase. That is ridiculous.
The whole thing is so self-imposed. "Well they don't want to make WiiWare titles because the size restriction." "So why have the restriction?" "Well we have to because we don't have enough internal storage." "Why don't you have enough internal storage?" "We wanted to cut down on costs." "Well why don't you allow the users to attach a hard drive at their own personal cost?" "Uh, because we don't want to?" You trace it all back and it always rests on some decision made by Nintendo either to cut corners or for, whatever insane reason, to prohibit flexibility or options. And it is always something that any intelligent sane person can spot the potential problems of a mile away. So Nintendo is either stupid, lazy, indifferent, cheap, malicious or insane. There is no way they could care and know what they're doing and get these results.