I don't know how many times on this site I've seen people state that the larger the install base leads to the largest profit. I've also seen the argument, "such and such million selling PS2 game sold poorly considering the 120 million install base." Well here's some data from the latest Japanese sales charts that show install base isn't everything.

http://kotaku.com/5043640/japanese-gamers-love-soccer-hate-new-square-enix-ip

2 new releases from highly reputable companies that are well loved in Japan sold quite poorly.

Inazuma Eleven (DS) - 41,000 / NEW by Level 5

Sigma Harmonics (DS) - 23,000 / NEW by Square Enix (Yohinori Kitase is involved in this game too which brings a lot of credibility to title.)

So everyone who thinks the Wii is automatically going to get a ton of games b/c of it's huge numbers or anybody who thinks games are going to start drying up on other lesser selling systems, think again. Install base isn't everything.

It sure aint.

I'd say it's more about the quailty of the games more than anything.

I can't tell you whether or not those games I mentioned are good or not, but that's why I mentioned the developers. I personally can't think of a bad Level 5 game, and b/c of the Professor Layton series, they're quite popular in Japan. Square is another company that usually releases solid games, especially if Yoshinori Kitase is involved. So going off reputation, these are probably pretty solid titles inspite of which didn't sell well on a system with a huge install base. This is why you still see a sparse few developers throwing quite a bit of support at the PSP (Square Enix comes to mind).

The DS has the highest software sales the Japanese market has ever seen. I don´t understand your point?

 Yes the DS has sold a ton of copies of games. Yes, the DS has the largest install base ever in Japan. Neither of those two things means that an individual game is automatically going to sell really well even if it is a good game from a highly reputable developer. That's the point.

That's also why you don't see all devs jump ship from 360/PS3 development to the Wii. Even when the Wii exceeds 50% of the market, you're not going to see this happen.

The reason why those games sold poorly was because they weren't marketed very well or weren't hyped very much

 Wow. if I'm running a developer, like say Square Enix, what the hell do I care if 200 million cartridges have been sold? Is the money from those sales going in my pocket? NO. My goal is to sell as many copies of the game I've developed. That's the big picture. Many people assume a 75 million install base and 200 million pieces of software sold means any good game that is released on the system will sell well. I'm showing you that that assumption is not only flawed, but is actually false.

I think you think that I'm trying to knock the DS for some reason. That's not the point. I realize the DS has sold a ton of hardware and software and that's great. But those good sales don't mean it's always a good idea for me the developer to release my game on the DS and avoid any other lesser selling system.

Well the point of OP is faulty like others have point out BUT
on the question about support to the various platforms I think he have a point althought not entirely sound.
What I mean is that Wii is NOT a PS2 ( it isn't mean to be ). So a huge install base doesn't traslate to a huge third-party support "stolen" to competition like previous generation.

The point is that this a uncommon generation where a contender ( Nintendo ) is succeding to change the context of the market ( paradigm shift ).
Develoers and publishers ( and products ) that don't suite to the new set of values brought by Nintendo will never be a good suit for DS or Wii.
The cardinal point of Disruption however is that the disruptor has a better ( more profitable ) business model thanks to the inclusion of new value at low cost ( remember key word here is "good enough" ) and the exclusion of costly values that have surpassed the desiderable curve for most consumers.

In this landscape the huge success of Wii will likely brought a damage NOT to PS3 or 360 but to their old way to conceive the market ( the previous status quo ).
Publishers early or later should adapt.
"Innovate or die".