Well I think D:DoC might be a good start, since Nintendo is working on it (right?), so quality is pretty much guarantee, and it will probably be marketed more (though Nintendo should do this for more 3rd party games).

But I don't really think mature games don't sell well on the Wii. I think it's more like, there aren't many mature games on the Wii to sell well. Here is a list of M rated games and their sales, with the highest ranked game (according to GameRankings) first:

I was going to do 10, but... there aren't even 10 games that either have sales data for them (unless I missed them), or have been released (House of Dead 2&3 just got released). I mean, there's seriously a lack of good games that are Mature. It's also worth noting that the Godfather games on any system haven't done steller (if the sales data is up-to-date and correct), and Godfather and Scarface I believe were both launch titles, which probably effected sales a bit. For reference as well, RE:UC average score (on gamerankings) is 75%, which sort of shows the quality (or lack) of decent M rated games. RE4 & RE:UC both have the RE name, so they were bound to sell decent, though RE4 is a port, and UC is a on-rails shooter. I believe RE4Wii has past RE4 GC, so that shows there's a audience for these types of games. NMH is a small market game, and has only just been released in Others, and I believe that Suda51 has said they've ship close to 400k of the game, which was good enough for them.

As for Teen rated games... Top 10 according to GameRankings:

And honestly, this list is hardly better. And after that you have Red Steel, DQS:MaskedQueen, Link's Crossbow Training, CoD3. Nothing stellers (or at least up to par with the likes of SSB:B  or even MoH:H2). TC:NB is missing Others data (might not be release there yet?) which could easily add another .2 to it, since the first one sold the best in Others. MoH:H2 is missing Others data, as does BW2. As for Marvel, the 360 was the only version to hit a million (and it was bundled) with the PS2 sitting at .61 million and the PS3 sitting at .22 million. All are missing Others data.

I know a few will look at those and say "well those aren't decent sales at all!" I hardly excuse the fact that MoH:H2 sold only .18 (and is probably at .25 or so with Others). But it wasn't advertised a cent as far as I know. Same with many of this games. I think once Nintendo gets supply under control (which I believe they will come the start of the new fiscal year) they'll start advertising some 3rd party games. Also i think once some 3rd party games start coming out that are worth advertising (not that some of those games weren't worth advertising, but they don't really deserve a big marketing push, since their sales will hardly justify it), we'll start seeing higher sales for these types of games. This will probably occur around Christmas (since many 3rd parties are still scrambling to get AA games out).

Depending on when D:DoC comes out, and it may be shown at E3 with a holiday release, it could be the start of the sweep of AA/AAA type more "mature" games for the Wii. Course then everyone will just say "only Nintendo mature games sell on Nintendo consoles" even though my list above clearly shows that decent games will get decent sales.