there are mixed answers on this, some say verbatims don't work for them and sony works just great, but most would say that verbatim made in japan/singapore is still the best to go with. dvd-r media. taiyo yuden premium line TYG02 TYG03 is also a very good one to go with, look for made in Japan for that one though.
The problem with media is the wii can usually read them initially, but it could be stressing the laser and overtime it will become weaker. Using good media from the start is the best way to do it.