Since in the past few pages I've seen several posts with comparisons involving the Wii, I think it's a much less black/white situation than what it's being portrayed here. I think I've already stated my opinion on the matter a few threads ago, but I suppose I could try to make my point clear enough again.
Hardware sales
The Wii in Japan wasn't the major success it represented in the rest of the world. Oh sure, for several months it just couldn't stay on shelves for too long, and it was doing extremely high weekly numbers (around 60,000/70,000 units), with games like Wii Sport and Wii Play being long-lasting huge sellers. But it didn't last nearly as long as in Europe/US, with sales in late August/September already showing signs of weakness, also due to an important lack of notable games between Mario Party 8 (July 26th, 2007) and Super Mario Galaxy (November 1st, 2007), and the latter had problems in selling out of the gate (later advertising initiatives solved this, though).
Wii Fit in late 2007, Super Smash Bros. Brawl and Mario Kart Wii in the first half of 2008 brought excitement around the platform again for a while, but starting by September sales slowed down again and the Holidays uptick was not as good as in 2007, due to less impactful releases.
And since the lack of relevant releases continued for a while, hardware sales decreased even further, with sales almost costantly under 20,000 units starting from the end of February. Wii Sport Resort and later on Monster Hunter 3 helped (the former with a more diluted, longer-lasting impact; the latter with a major single uptick), but again, not enough to stop the console from going under 20,000 again around September. NSMBWii was a major seller, and that contributed to an incredibly healthy Holiday in 2009.
2010 saw sales improving compared to 2009's first few months (thanks to NSMBW's lasting effect), but it couldn't last forever, and 2009's Holiday heights couldn't be reached for obvious reasons. But it was already 2010, and the sales later in 2011 halved, due to internal attentions shifting to 3DS mainly + third èarties focusing more on PS3, PSP and starting to release some games on the 3DS itself.
Basically, the Wii in Japan has never showed the same signs of strength that we've seen in the rest of the world, if not for a much, much, much shorter period, in spite of several major successes on the platform.
Software sales/support
If we're speaking of third party support, we can't say they were completely innocent for what happened with the Wii: unfortunately, it was just in 2009 when several major titles (Monster Hunter 3, Samurai Warriors 3, Tales of Graces + FFCC: The Crystal Bearers) showed up on the system, instead of stuff here and there as it happened earlier in its life. So, there's no doubt that 3rd parties were slow in developing important games for the system - but thinking this was the only problem would be an extreme oversemplification of the entire situation, especially since it would pin responsibilities on just one side. Instead, we just need to look more carefully at software sales as a whole, and we discover that...the Wii was not a software juggernaut as it was in the West, especially if we're talking about more core releases (kind of a similar trend, don't you see)?
Of course it saw several good results early on (Dragon Ball: BT2's late port, Dragon Quest: Sword, RE: The Umbrella Chronicles, and RE4: Wii Edition on a lower scale), but it also showed problems at selling games from less known franchises, and JRPGs as a whole seemed to not be a good fit, sales-wise. Major brands? Early on, it didn't have problems in doing so. More casual-oriented games? The Taiko franchise was a good-to-great seller, depending on the entry, as well as Go Vacation and Fishing Resort, despite their 2011's release. But nicher, more core stuff? Arc Rise Fantasia, Muramasa, Fragile, Tenchu 4, Harvest Moon games, Rune Factory Frontier, etc.etc. It also had problems in selling yearly iterations of sport games: not that Konami isn't completely guilty due to how they handheld the PES franchise on the system, but sales going down so quickly iteration-after-iteration wasn't just due to bad planning. See also the Pawapuro series to see how Wii SKUs kept on selling lower than PS2's despite several efforts (online play, lower price).
Basically, it seems like the early efforts in attracting a more casual, more mass-market oriented audience worked maybe way too well, in such a way that there was a very limited audience for more mid-tier games / franchises, with some exceptions. And then 2009 came, with the Crystal Bearers' disaster and Tales of (dis)Graces - the latter was a major sign of the JRPG audience basically rejecting the system.
The market's context
Also, another factor we need to consider is the market itself at the time. When we think of the Wii in the West, we remember a record-smashing system, with incredible hardware and software sales, at the top of the charts alongside the DS. Or just the top selling system if you consider just the home consoles. In Japan, it was the second best selling system for a while, and then it became the third best selling sytem when MHP2ndG exploded even further than the original. Yes, in Japan you just can't shrug off DS and PSP saying that they're handhelds, thus a different market. Nope, it means constructing an entirely untrue context, because in Japan all the systems were fighting for support, not just the home consoles. And, well, the Wii released when the DS was already a phenomenon, with over 100,000 units sold per week and being an extremely attractive proposition due to DQIX as recent announcement.
PSP was also starting gaining some ground in 2007, even more in 2008. This is why the Wii couldn't get enough third party games, there were two other systems (at first, mainly the DS) that attracted lots of attentions from developers, and for good reasons. Again, of course third parties should've been quicker in releasing relevant Wii games, but it's also true that probably Nintendo didn't do enough to court them, aside from offering to them a system with great early sales - but it wasn't enough when Japan had another system with even bigger sales and another system with good sales and that was starting to gain some third party potential (MHP2nd, Crisis Core). Plus, Western-focused development was on PS3 and 360 initially - heck, the whole batch of 360's exclusives partially delayed things in the greater context (remember all Microsoft's efforts for the Japanese market back then?), and the Wii was both power-wise and architecture-wise a platform that couldn't easily accomodate multiplatform development, unless you had specific teams dedicated to create Wii-specific version of games. Thus, efforts came when it was too late to improve the audience's situation.
Later, I'll discuss why and how I believe the current Switch situation is pretty different. This post is already long enough
