The raw ISO contains a lot of "dummy data" (empty sectors used to push game data to the faster outer edge of a physical disc). A standard compression tool like WinRAR or 7-Zip can strip this dummy data, reducing the file from 4.37 GB to roughly 1.2 GB.
Many sites claim "Download ISO" but give you a 2 MB Downloader.exe. Running this infects your PC with adware or ransomware. sonic unleashed wii iso highly compressed
No article on "highly compressed ISOs" is complete without the legal disclaimer. Under the Digital Millennium Copyright Act (DMCA) and international law: The raw ISO contains a lot of "dummy