RetroPie allows you to turn your Raspberry Pi or PC into a retro-gaming machine. It builds upon Raspbian, EmulationStation, RetroArch and many other projects to enable you to play your favourite classic games with the minimum set-up.This app doesn't have any features at the moment.
Lakka is the official Linux distribution of RetroArch and the libretro ecosystem. Each game system is implemented as a libretro core, while the frontend RetroArch takes care of inputs and display.
batocera.linux is an operating system (like Windows 10 and Mac OS) specialized in retrogaming available for your pc and different nano computers like the Raspberry and the Odroids. Note that you must own games you play in order to respect legality.