I have tried Okami on a modified Wii with a standard setup using a wad channel and cIOS in my zip installed and nothing else.
It was burnt to a Philips DVD-R at 4x and 1:1 and it worked fine.
Have you confirmed that the ISO you have is ok ? That may be where the trouble is if only that disc cant be read.
I have a PAL wii and used a PAL version of the game with no issues in gamma - had a lot of problems in the beta version , but none in gamma for this game.
It was burnt to a Philips DVD-R at 4x and 1:1 and it worked fine.
Have you confirmed that the ISO you have is ok ? That may be where the trouble is if only that disc cant be read.
I have a PAL wii and used a PAL version of the game with no issues in gamma - had a lot of problems in the beta version , but none in gamma for this game.