RetroArch is a graphical frontend for emulators, game engines, and media players.
VisualBoyAdvance (VBA) is a free software (GNU GPL) emulator targeted for the Game Boy, Super Game Boy, Game Boy Color, and Game Boy Advance handheld game consoles sold by Nintendo.Discontinued
The project is no longer developed. Last version, 1.8.0 beta 3, released in October 2005, can be still downloaded from FileHippo
VisualBoyAdvance vs WinDS PRO opinions
Open Emu is an open source project to bring game emulation to OS X as a first class citizen, leveraging modern OS X technologies such as Cocoa, Core Animation and Quartz, and 3rd party libraries like Sparkle for auto-updating.
Mednafen is a portable, utilizing OpenGL and SDL, argument(command-line)-driven multi-system emulator with many advanced features. The Atari Lynx, GameBoy (Color), GameBoy Advance, NES, PC Engine (TurboGrafx 16), SuperGrafx, Neo Geo Pocket (Color), PC-FX, and WonderSwan (Color)...
NO$GBA is a Nintendo DS emulator for Microsoft Windows. It is capable of running commercial and homebrew Gameboy Advance and Nintendo DS games, such as Pokémon Diamond which the latest version is able to run at full speed with no graphical glitches.
A front-end or user interface (UI) is the presentation and interaction layer of an app or website. Most modern emulator apps have basic game list UIs that you can interact with using a mouse/keyboard but not a game controller.
RetriX is an emulator front end for UWP, on all the hardware platforms it supports: it serves the same purpose as RetroArch but is built from the ground up to integrate as well as possible with Windows.