EmuNations

Playnite is an open source video game library manager with support for 3rd party libraries like Steam, GOG, Origin, Battle.net and Uplay. While providing one unified interface for your games, it includes game emulation support, fullscreen mode, themes and much more.

Requires Windows 7+ and .NET Framework 4.6 

QEMU is an open source machine emulator and virtualizer.
When used as a machine emulator, QEMU can run OSes and programs made for one machine (e.g. an ARM board) on a different machine (e.g. your own PC). By using dynamic translation, it achieves very good performance. 

MS-DOS Player is a MS-DOS emulator running on Windows (32/64-bit) command prompt. Its 16-bit MS-DOS compatible commands can be executed on Win32/x64 environments.

It basically inherits the environment variables from the host Windows, and a target command can access the host's file path directly. As such, you can execute 16bit MS-DOS compatible commands on your 64bit Windows in the same sence as you did on 32bit Windows, and you do not need to copy any files to/from a virtual machine (VMware, Virtual PC, XP mode, or others).

Note: This emulator DOES NOT support Win16 execution files. It aims to support character user interface utilities, for example file converters, compilers, assemblers, debuggers, and text editors. For now, doesn't support graphic/sound hardwares nor is intended to support game softwares.

Wine (Wine Is Not an Emulator) is a compatibility-layer capable of running Windows applications on several POSIX-compliant systems such as Linux, macOS & BSD.

Instead of simulating internal Windows logic like a virtual machine, Wine translates Windows API-calls into POSIX-calls on-the-fly, thus eliminating performance and memory penalties and allowing you to cleanly integrate Windows applications into your desktop.

WineD3D For Windows is a DirectX 1-11 to OpenGL wrapper with almost full implementation of DirectX used in Wine. Even if Windows supports DirectX natively, using WineD3D can enhance backwards compatibility with older games, especially on Windows 8+ that don't support 16-bit screen modes. Others possible values include eliminating unsupported versions of DirectX, or porting DirectX applications to OpenGL without having to rewrite the rendering code. That said, it's far from perfect... 

EmulationStation Desktop Edition is an open source frontend application for browsing and launching games from your multi-platform game collection. It comes preconfigured for use with RetroArch and a number of other emulators. It's also fully customizable so you can expand it to launch other emulators or applications. It has several features such as minimal setup, full controller support, very customizable, Built-in scraper for downloading game info and game media, fully themeable and much more...

Utilities

• RetroBat is a software distribution supplied through EmulationStation interface and is fully functional and highly customizable.

Nostlan (formally Bottlenose) is a high quality front-end launcher for gaming emulators which supports Windows, Linux and MacOs. It's currently capable of launching more mainstream emulators with nice features and its future looks quite bright!

Current Features

• unified UI for mouse/gamepad interaction
• designed for UHD displays and projectors
• checks multiple database sites for the highest quality box art
• nostalgic UI themes for each supported console
• fancy scroll direction alternation effect on rows in cover view mode
• most controllers connect to Bottlenose automatically, no setup required including Xbox One, PS4 Dualshock, and Switch Pro controllers
• gamecube controller adapter supported with gca-js
• advanced customization: edit launch commands and change game art

86Box (formerly known as PCem Unofficial, PCem Experimental, or PCem-X) is an unofficial branch of the PCem emulator, which aims to run older operating systems and software designed for IBM PC systems and compatibles from 1981 through fairly recent system designs based on the PCI bus.

Features include but are not limited: Low level emulation of 8086-based processors up to the Pentium with focus on accuracy, Great range of customizability of virtual machines such as the very first IBM PC 5150 from 1981, or the more obscure IBM PS/2 line of systems based on the Micro Channel Architecture, Lots of supported peripherals including video adapters, sound cards, network adapters, hard disk controllers, and SCSI adapters and much more!

It is also recommended to use a manager application with 86Box for easier handling of multiple virtual machines:

• 86Box Manager - It's an optional configuration manager to create and edit multiple isolated virtual machines while running at the same time and much more...