Officially it's not possible, and for some reason Kirby's Adventure is horizontally scaled without filtering so it has scrolling artifacts. I know for a fact you can patch the dol so it scales correctly but I never tried forcing 240p, should work though.
Hm. That's a bit disappointing, but good to know.
If you want easy 240p you should go for the VC versions, but you lose wiimote support, the small borders and widescreen correction(geez Nintendo).
I don't quite know what you mean by "you lose wiimote support", but if that means I wouldn't be able to play the game using a Wii Remote itself as a controller, that's not a big deal for me. I have some
Raphnet Tech 4-in-1 adapters that let me use any pre-Wii controller as a Classic Controller, so I can use whatever controller the game used on the system it was originally released for.
(Well — minus the Game Boy ones, I suppose, but that hardly matters. I own physical copies of those Kirby games already, and a Super Game Boy and SGB2.
)
Widescreen correction isn't really necessary for me (at least, currently), since I don't have an HDTV — only a large, 4:3-ratio CRT television.
Personally I like having wiimote controls available, so I would just take the chance with patching 240p into the collection if I needed it. I don't like that KA and Super Star are really dark but the official VC versions are as well.
I'll have to look around (and probably ask on this forum) to see how one would go about patching 240p support into KDC; all I know is that games that originally ran at 240p resolution running in 480i resolution look… not quite right to me, for some reason.
I'm also a little leery of getting the official Wii Virtual Console version of Kirby's Adventure, because I've got EarthBound Beginnings on the Virtual Console for the Wii
U, and while the darkness isn't much of an issue for me… the improper overscan cropping it has
is an annoyance to me. (Instead of cropping the top 8 and bottom 8 pixels, it crops the top 9 pixels off… and nothing from the bottom. Good job, Nintendo.)
I don't know if the official NES VC games for the
Wii (or other Wii U NES VC games) have that cropping issue — I'm guessing they do, though —, or if it's merely a problem with EarthBound Beginnings, but it still annoys me. >:| (Seriously, Nintendo! Even
NESticle got the cropping correct! And it was
NESticle!)
I didn't know Kirby Super Star would be really dark, too, though. That seems kind of strange; I can understand why the NES VC games would be dark, but the Super NES had a hard-coded digital palette (rather than the analog wonkiness that the NES had), or so I'd thought. o.O