Well the whole "M rating" intolerance of Wii owners is a bunch of bull that people have latched onto. It's actually a cop out not a formidable defense. M rated games will sell on the platform, but developers have to give the buyers a reason to get them. They just aren't going to see the M rating and purchase just like they aren't going to see the M rating and not purchase.
Take the Cabela's 2010 game on Wii. Game was a perfect fit. Hunting game, came packaged with the rifle to better immerse the game, good pricing, and a large marketing campaign focusing on its core features. Beautifully done and Activision is seeing huge sales because of it. Game could have been rated M and sales would probably still the same.
Publishers need to learn from Activision there or Nintendo in general. If you want a game to sell you have to actually sell it. Especially with Wii which has a lot of competition for shelf space. You have give a reason for them to pick this title up, explain the features, hype it up before hand, and the advertise them quite well. Do that and the userbase will start to show. That's how Nintendo can polarize almost 10 million buyers to pick up a Mario game and sell to 1/6 of a userbase in less than 10 weeks. 3rd parties may not be able to accomplish that but that is something they should seek to mimic.
Of course it always come down to how much are you willing to spend. If you aren't willing to take the risk then you can't really complain. Not to mention if they aren't spending money on marketing it's hard to think they spent much on the game meaning some of these sales should make them quite profitable anyways. But if they want a breakout success they need to first make a quality title that has good features, hype those features up, then sell those features in the marketing.
