@Neal & broodwars
Let's not forget that if it was financially sound for every (3rd party) game to be on all platforms, then they would be. In fact, by that logic, every third party game without an exclusivity deal would be on the Wii. Just compress some textures, scale down the resolution, strip out the fancy lighting effects, decrease the draw-distance. Bang. Zero effort Wii port!
... I hope the absurdity of this example is not lost on anyone.
You seem to assume that if companies put these games on Wii, they'd actually sell. I think Wii 3rd party sales have shown that is not the case. But be that as it may (and there are valid Pro-Wii arguments as to why that is), it's a
lot more work to create a Wii version of an HD game than it is to take a Wii game and up-res it for PS3/360. If you create a Wii version, you have to do the things you already stated
as well as practically remaking all the building and character models with
much lower poly versions to deal with the Wii's stone-age technology. I'm sure that's acceptable if you have a Big Name game like Call of Duty or if you're going to make a PS2/PSP version anyway, but I don't know why you'd go through all that work and cost otherwise, especially when the Wii's practically dead right now anyway. Oh yeah, and throw in Nintendo's Certification process for good measure...
On the flipside, as we saw with Dead Space Extraction and many of the HD re-releases of PS2 games, when you bring these standard definition Wii games into HD, you just swap out the textures and optimize performance and you have something you can sell for cheap on the download platforms in probably 6-8 months. Now, if a company wants to get fancy (as those screenshots from Overkill seem to suggest, as well as what I've seen of No More Heroes HD), you can add more effects and whatnot to sweeten the deal, but the bare minimum it takes to have the game
function on the platform is already dealt with and you're pretty much mostly re-using assets you already have rather than having to create new ones.
On reflection, actually, I wouldn't be surprised if we saw these HD re-releases on the Cafe as well once Nintendo releases the appropriate hardware with perhaps a quality download service.