GameCube/Wii discs already use fairly dense data. Most of the size comes from actual game assets – textures, audio, models. You can’t compress a racing game’s track files to 1% of their size without breaking the game. That’s why in the best cases.
Rather than looking for "highly compressed" ISOs or RAR files (which can often lead to corrupted data or crashes in games like Paper Mario The Legend of Zelda ), the Dolphin team recommends using Why it works dolphin games highly compressed work
Leo learned that while he couldn't shrink Wind Waker to 50MB, he could convert a standard ISO into an NKit format, reducing the size by roughly half (from 1.3GB to roughly 600MB) safely. GameCube/Wii discs already use fairly dense data