If you are looking to save space on your Android device legitimately , the best method is not downloading sketchy "highly compressed" files from random sites. Instead, use the format.

Are you currently experiencing ?

While many sites offer "highly compressed" downloads, they are often just standard ISOs in a ZIP or 7Z archive that must be extracted back to full size to play. To actually save space while playing, you should convert your ISOs to : Compress Your ROMs on Android with CHDroid!

The absolute best option for Android is (a community-updated version of the legendary, discontinued AetherSX2). It offers incredible performance, widescreen hacks, and native support for compressed formats.

Compresses excellently from over 4 GB down to around 1.3 GB.