I'm sorry but gamecube games on wii can't be played in 480p resolution, they only go up to 576i.
Yes they can, it just depends if they support 480p or not. For example, I play Wind Waker in 480p all the time.
I played MGS: Twin Snakes but it only went 576i, that's unfortunate because the game could have been better in 480p. Does Wind Waker go 480p even on a wii PAL ?
I don't have any PAL GC games, so I don't know.
AFAIK, PAL games don't do 480p games, but most NTSC games do, included Zelda WW, F-Zero GX, Super Mario Sunshine etc.
Unfortunately, European GCs just don't have that 480p option, there's nothing you can do about it ( short of a firmware hack maybe ).
Much easier to get a used NTSC GC and some progressive cables ( the equivalent of component cables for the Wii ), and start to collect NTSC games.
Remember, in 2001 an NTSC GC wouldn't work in Europe ( and not just for the different voltage , 110v vs 220v, easily overcome by getting an european AC adapter ) but also because only a few TV sets were able to accept a 60hz signal, most were stucked at 50hz still.
Now that almost everybody on the planet has HD TV, most of which run at 60hz, there is no problem in running NTSC content on an European TV in full color at 60hz.
Another option, would be to run those NTSC GC games on a Wii. If the Wii is connected to the TV with component cables, and the GC game in question supports progressive mode ( there was a Wiki list somewhere but I don't have the time to look for it now ) then you will be prompted to activate 480p (progressive mode ) upon booting the game automatically.
But remember, it has to be an NTSC game, there is no such thing as a PAL game running in 480p.