LaunchBox - LaunchBox is a portable, box-art-based games database and launcher for DOSBox, emulators, arcade cabinets, and PC Games. Download it free!
Playnite - Source code generated using layoutit.com
Photon Game Manager - Photon is an advanced game launcher that is designed to make your game collection look amazing.
QuickPlay - Quickplay the universal emulator Frontend
Lutris - Lutris is an open source gaming platform for GNU/Linux.
GOG Galaxy - Truly gamer friendly, DRM-free online gaming platform.