RetroArch is a graphical frontend for emulators, game engines, and media players.
RetroArch vs D-Fend Reloaded opinions
It is an emulator and not a frontend, so Retroarch is in the wrong section being recommended here.
D-Fend is a Frontend while RetroArch is an emulator.
LaunchBox was originally built as an attractive frontend to DOSBox, but has since expanded to support both modern PC games and emulated console platforms. LaunchBox aims to be the one-stop shop for gaming on your computer, for both modern and...
LaunchBox vs D-Fend Reloaded opinions
Because it is more feature rich and compatible with recent dosbox versions.
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.
Boxer plays all the MS-DOS games of your misspent youth, right here on your Mac.
The project is no longer developed. Last version, 1.4.0, released in February 2016, can be still downloaded from the official website
HyperSpin is an animated arcade frontend for Windows for use on Home Arcade Machines. HyperSpin allows you to create custom menu systems to run most executables with that arcade look and feel. HyperSpin takes a more artwork oriented approach to creating menu's.
QuickPlay is a windows powerful universal emulator 'frontend-of-frontends', which has support for countless emulators and systems, old and new, with a philosophy of being quick and easy for new users, yet comprehensive and flexible for old-timers.