i'm sorry you feel that way but let me just put together a few pics of the top 3's biggest franchises.

Nintendo:

Microsoft:

Sony: 

...so no, that was not code for retarted.  it was code for nintendo has a different artistic vision then MS or Sony.  if you can't look at those screens of the biggest franchises each developer is bring to the market i suggest you go take an art class.  it's not like this is a SD vs. HD thing...this difference in artistic vision was just as present last generation when the game cube had more power then the ps2.

The ultimate thread killing point in this whole 'massive userbase should equal massive hit' argument is the PS2. It's the best selling console of all time, it's got one of the best gaming libraries of all time and it's sold more software than any other console. But it doesn't have any games with twenty million sales, and only five with more than ten million.

Meanwhile, five different Nintendo consoles have games with twenty million sales or more, four of them have several games with those kind of sales, with only the SNES having just the one game at that level, and yet none of those consoles beats the PS2 in userbase size. In fact the PS2 dwarfs several of those consoles.

What's that I hear you say now? The higher the userbase the more diversified the sales are? Doesn't that support the argument of the OP?

I don't know about that, milky.

Most of those 20 million sellers were bundled games.

Also, take into account that there was a ps2 slim, and that ps2s had a pretty high failure rate. From what the critics say, the ps2 had the kind of failure rate 360 had. So when you're talking about the ps2 userbase over ten years of sales, keep in mind that at least half of them don't work anymore. However, wii has like a 1-3% failure rate, which is substantially better. But, I will accept that there are probably a good amount of wiis in old folks homes and sitting on shelves as raffle prizes. :P

A high userbase does not equal diversity. It can sometimes lead to diversity, but it isn't automatic.

I think the problem with 3rd party games on Wii is really two fold.  

(1) AAA games from AAA developers for the most part aren't going to the system, and never have been.  Now we do have a few high profile counter examples (MH3, DQX), but we've never really had a situation like this, where the overwhelming market leader doesn't get the overwhelming market support.  What Wii seems to to attract is largely B-tier brands, spinoffs, shovelware and niche games, the games are generally badly or unpromoted and budgets are generally lower than even last gen on PS2/Xbox/GC.  It's bizarre, and even stuff like viable PSP ports that would likely do better  on Wii (Soulcalibur BD, Kingdom Hearts BBS, etc) aren't materializing.  It's like the industry wants Wii to fail, like publishers are actually fighting the will of the marketplace, and I'm honestly at a bit of a loss to explain it. 

(2) Robust 3rd party support didn't come fast enough, and as such didn't build markets to support core oriented games as should be expected by the overwhelming market leader.  I think Samurai Warriors 3 makes a great example of this... the game sold over 250k in Japan, which evidently didn't hit Koei's expectations for such a high profile release, but the real issue here was that they'd already built that Musou audience on PSP/PS3, and this was Wii's first legitimate Musou game coming a full 3 years after launch.  By comparison PSP got it's first Musou at launch (and it also sold around 250k), PS3 got it's first Musou less than six month after launch (sold 300k and carried the popular Gundam license) and even 360 got it's first Musou less than a year after launch (it bombed but well... it's 360 in Japan).  The problem here wasn't that Koei bothered with Musou on Wii, the problem was that they did it 2-3 years late... and really this story is emblematic of 3rd party Wii games.  You look at the first year and we saw quite a few notable 3rd party success stories (Red Steel, COD3, RE4, REUC, DQ Swords, Sonic SR, etc), but that wasn't really followed up on or supported fast, frequently or just well enough.  I think to some degree that market got tired of waiting and moved on.  And honestly, this problem may be more of a "too late" situation, the only question in my mind is if 3rd parties will fall asleep at the wheel and make the same mistake next generation...

You can make a credible argument for Wii Sports and Wii Play, as they come with standardized hardware.  For Mario Kart or Wii Fit though, you really can't... in the latter cases it's unquestionably the software driving these sales.  And honestly, Wii Sports drove plenty of hardware purchases itself among the mainstream.

I believe that the real problem is demand destruction. Third parties had a pivotal hand in shaping the Wii's market from the very beginning. Unfortunately, by flinging barrages of shovelware at the Wii while putting their best efforts on the competing systems, the Wii's market has been shaped in such a way that excludes third parties. It goes like this:

Those who stay Wii-only owners, see that third party games on the Wii are almost always crap, and learn to avoid them.
Those who own multiple consoles, see that third party games on the Wii are almost always crap, and end up getting their games on the PS3 or 360 instead, which represent their best efforts.

Basically, third parties screwed the pooch on this generation, big time. They blocked themselves off from half of the entire console market, a new untapped market, in favour of the existing, but increasingly cutthroat and parochial half. By now, even if third parties were to change gears and produce their best games on the Wii, their sales would be low, because they managed to destroy demand for their games on the Wii so effectively over the past three years. Meanwhile, Nintendo continues to hoover up the cash, completely heedless to the existence of said market, or lack thereof, on their own system.

It looks like we tried to make the same points at roughly the same time >_>

I agree with Rol, Jarrod, and Kenny.

Also I'll add that this sort of behavior is not anything new. It happened during the NES era. But I will say that any business or company that blames an audience for their product not selling will not be in business much longer.

It's an issue of investment, too. 3rd parties bet the farm on HD development, pouring millions into making engines for these games well before anyone was aware how this generation would actually turn out, and they're trying to stick with what they have. It would look really bad to investors if the 3rd parties came out and admitted that they could have made similar amounts of money without having to pour so much into cultivating new development assets.

That also explains the "multiplat everything" strategy that you see. 3rd parties chose to play in the space that ended up being the smaller space, where they simple couldn't survive unless they spread it out as far as possible across that space, leading to the concept of the "HD Twins" with "mirrored libraries." That's Wii's fault, since you see games that would have stayed exclusively Xbox (like BioShock) or exclusively Sony (like Devil May Cry) have to go across

I'll agree on the bafflement about them not making some no-brainer PSP-ports, especially of that Soul Calibur game. My guess is that has to do in part with PSP's strength in Japan, that for Japanese publishers it makes little sense to do PSP-to-Wii ports, since you're porting to a console with a smaller install base from their perspective. The more insulting thing is with the western third parties that make PSP ports (Army of Two 40th Day and Dante's Inferno come to mind here), when it would clearly have been to their advantage to make a Wii port instead, given that PSP can't move software to save its life in the West.

Well, I agree with 3rd parties betting it all on "HD", and that in part explains their slow turnaround.  My issue is more that there's been no actual market wide turnaround, they're just going ahead with "HD".  Even in previous generations where we had an unexpected market shift emerge (NES, PlayStation) you saw the industry eventually switch gears and move to correct for that shift... we haven't gotte that this generation, and it looks like we won't be getting it either. :/

The other end of this is DS, which has pretty much taken the bulk of Japanese support that I think Wii would've inherited.  Japan's weird... DS gets most of the mainstream stuff, PSP gets most of the otaku stuff, PS360 gets most of the stuff for overseas, Wii gets left with nothing.

As far as PSP games, I'd agree in some instances the JP market target makes sense (Gundam Vs Next, Valkyria 2, Absolute Hero, etc) but games like Soulcalibur or Kingdom Hearts are made more for an international audience, and do substantially more of their sales in the west (where PSP's basically a dead format for software).  Those sorts of games would more than double their worldwide sales with a Wii port.