Use an app like ZArchiver to extract .RAR files into .CSO format.
If you are gaming on a budget device, dealing with a small memory card, or working with a slow internet connection, highly compressed PSP games are your best solution. Through advanced compression techniques (like converting ISO to CSO or DAX formats, and stripping out non-essential data like dummy files, foreign audio languages, and uncompressed video trailers), massive titles can be shrunk down significantly.
These games are either naturally small or commonly available in highly compressed formats that maintain smooth gameplay on the PPSSPP emulator Jetpack Joyride
This game brings fast-paced, high-flying anime combat to your screen. It features a robust roster of fighters, smooth 60 FPS animations, and an engaging storyline based on the Janemba movie. Grand Theft Auto: Vice City Stories (Super Compressed) Compressed Size: ~70MB – 90MB Original Size: ~800MB+