no only ssbb is dual layer.
dvd5 means its the stripped down version so it goes on a regular dvd-r
the discs that are dual layer will say they are on the spindle, they usually cost $2-$3 a disc.
If your system is an NTSC wii then its possible that brawl may not even work for you depending on what chip you installed.
Just saw youre in auckland, so youd have a PAL system. Could also just be your burn. try a different game first see how that goes.