OK, now I can report that I was at a friend's house and he has bought a pre-modded Wii. He had both NTSC and PAL games burned on DVDs, i.e. not originals. And they both worked perfectly on a North American Wii and LCD television set.

But I'm not sure if a PAL game would work on an unmodified Wii. If they would, why are there NTSC and PAL versions?