Emulator

Nintendo doesn't have the same situation (with mapped PC controllers) as us, which is why they haven't done much to prevent this problem. In other situations, like using the Wii U GamePad with vWii, they do tell users that the GamePad won't work every time they press a button.

Not having any controllers configured by default sounds fair. As it is now, you essentially already need to visit the controller config before you start playing, unless you know the default keyboard mappings by heart and are comfortable with using them.

You could have icons for the supported controllers displayed in a "Supported Controllers" column in the game list, like how Wii games show the supported controllers on the back of the box. A message box is just obnoxious.

Just commenting saying if this is done with data from the wiki it's all already there ready to go. The wiki's ID information is really good (the best source for Gamecube/Wii IDs on the internet as far as I know), and I think most of the input methods listed in the infoboxes come directly from Nintendo's website, so those should also be highly accurate. The only IDs that are known to have any problems are digital Korean IDs, they shouldn't use a K region code. They're supposed to have region code T apparently, it's just nothing's been done about it yet. See https://wiki.dolphin-emu.org/index.php?title=User_talk:Xerxes/Archive#JALT01 for details on that. If the Korean digital IDs are fixed then I'd say the wiki is in the 95-99% accurate range for IDs. Won't speculate on input method accuracy but I'd go as far to say it's above 90%, take that with a grain of salt though.

To be more specific, Korean titles use K when they're in Korean, Q when they're NTSC-J VC imports and T when they're NTSC-U VC imports. (Regions other than NTSC-K also have specific letters for VC imports.) I don't know if there are any NTSC-K WiiWare titles, but if there are, those probably use K.

THANK YOU!! I just saw this. You solved the mystery!