While compression technology exists (like ZIP or RAR archives), it has limits. Most modern games are already compressed using advanced techniques by the developers themselves. You simply cannot mathematically compress a complex 3D open-world game from 7GB down to 50MB without removing essential data (like cutscenes, audio, or textures).
The raw copy of the physical disc. It includes dummy data, making even a 500 MB indie game appear as a ~7 GB file. xbox 360 roms highly compressed
Move the files to your FAT32-formatted USB drive or internal hard drive. While compression technology exists (like ZIP or RAR