On the one hand people say that publishers "left money on the table" by not developing "core" traditional titles for the Wii.
They did, if they would've gotten them out early. By 2009 and later, most of that audience had given up hope in waiting, though.
When they did though these weren't generally met with a lot of success*.
Pre-2009 examples of actually trying?
RE4 sold amazingly beyond Capcom's expectations, and they followed it up with lightgun games. COD3 sold better on Wii than PS3 from launch, yet COD4 (the game that really catapulted the series) skipped Wii in 2007.
There wasn't a large audience for their games, despite the large installed base.
There was at the beginning.
So in actuality did they leave money on the table?
Yes.
They did meet success when they developed titles geared towards the "casual" expanded audience market that Nintendo actively cultivated on the system;
Yes, but they could've had both, if the industry had supported Wii like the market leader.
At which point, the argument becomes that third parties should have developed an audience on the Wii, presumably by releasing titles regardless of commercial return/opportunity cost? But then the question is: Why - why sink money and resources into developing title after title to develop an audience; when the audience is already available on other platforms that are easier to work with.
You mean PS2? Yeah, why ever try to develop games for a new generation, when your audience is already on the old generation machine. It doesn't make any sense!
You're basically arguing for never trying to find an audience on multiple devices. However, that's incredibly short-sighted and rightly seen as stupid. At the beginning of a generation, the audience can be shaped by what you push on it. Yes, Nintendo pushed Wii Sports, but they also pushed Zelda and Mario Galaxy. RE4 was a great success, and they followed it up with an on-rails shooter and never brought RE5 to the system.
The point is that 2009 and later, yeah, the core audience on Wii had shriveled up due to lack of feeding. 2007/2008, it had great potential to be a good source of sales for core games, but the games didn't come. Many people try to rewrite history by focusing on the 2009 and later lack of success and saying that the audience was never there to begin with.
And why is there no onus on the platform holder to do so?
There's the rub. Nintendo should've absolutely done more to get publishers to bring over those early core titles to the Wii to be "umbrella" games to help build the audience better on Wii and convince more scared publishers to take the "risk" of putting their games on Wii, too. Nintendo apparently thought that providing the largest single userbase would be enough (Hey, it worked for PS2!), but with their hamstrung power in the system (No, it won't be the same this generation, since there were core architectural differences beyond simply power concerns), it became too much of an effort by publishers to put basically whole teams in play to try to create the same game on such vastly different hardware. Add to that the massive loads of FUD surrounding the Wii when it launched (even see such nominally level-headed press like Steven Kent going off the deep end from it), and they had more than enough reason to "pass" on any Wii versions. That's where Nintendo should've stepped in to provide incentives to bring over,
at least, those big "umbrella" games. They didn't in time, and the Wii's industry supported withered before ever really bearing much fruit.
That's what I don't want to happen with Wii U. Nintendo needs to take whatever steps they need to to prevent an industry support repeat from Wii. They seem to be on a good start (matching advertising some launch games, really low digital cuts and supporting digital+retail Day 1 releases, open online that should be more account-based than Friend Code based), but time will tell if it (and further needed efforts) worked.
