A standard Wii disc dump is about (DVD5). “Highly compressed” versions shrink that to 100–400 MB by:
For the safest experience, it is recommended to dump your own retail disc using a homebrewed Wii and convert it to for a balance of space-saving and data integrity. legally dump and compress your own Wii discs using a homebrew setup? sonic unleashed wii iso highly compressed
This is the gold standard for playing on actual hardware. It automatically removes the "padding" from the ISO. The Ultimate Guide to Sonic Unleashed Wii ISO