Ppl have varying success. The most popular for Wii is Verbatim DVD-R. It should be the first you try. Some use TDK & Sony and there are others that can work. Only use imgburn and usually @4x speed - though increasing or decreasing the speed can help on problem burns.
I have used Memorex 16X DVD+R, Verbatim 16X DVD+R, and Memorex 16X DVD-R, all printable media with 100% success. For Brawl I used GQ DVD-RDL with 100% success.