EmuNations

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... 

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. 

dgVoodoo is a wrapper for old graphics APIs to run on modern Windows operating systems. Its applied using Direct3D11 with different types of wrapping outputs:

• Hardware rendering at GPU feature level 10.1 (recommended)

• Hardware rendering at GPU feature level 10.0 (there are some restrictions)

• Software rendering through Microsoft WARP renderer

The API's it currently can wrap are:

• Glide 2.11, Glide 2.45, Glide 3.1 and Glide 3.1 Napalm

• DirectX 1-7 (all versions of DirectDraw and Direct3D up to version 7)

• Direct3D 8.1

You also need the 3Dfx splash dlls for Glide if you want 3Dfx splash screen or watermark (shameless plug) through dgVoodoo. 

• 3DfxSplashDlls.zip

You may also need D3DRM.dll (Direct3D Retained mode) for some games and demos. It's not part of the OS since Windows Vista.

• D3DRM.zip

DOSBox-X is a free and cross-platform DOS emulator for running DOS games and programs. Started as a fork of the DOSBox project, it retains compatibility with the wide base of DOS games and DOS gaming DOSBox was designed for. But it's also a platform for running DOS applications, including emulating the environments to run Windows 3.x, 9x and ME and software written for those versions of Windows. DOSBox-X aims to be a complete DOS emulation package that is both fully-featured and easy to use, covering all pre-2000 DOS and Windows 9x based system scenarios. 

While they have made efforts to maintain and improve the emulation accuracy of the hardware and many more ways to configure the DOS virtual machine, they also try to strike a balance between emulation quality, speed, and usability, including improving the out-of-the-box experience for new users who want to run DOS programs or games, as well as implementing emulation that is accurate enough to make retro-programming possible with confidence the program will run properly on actual hardware.

ScummVM is a program which allows you to run certain classic graphical adventure and role-playing games, provided you already have their data files. The clever part is by replacing the executables shipped with the games, allowing you to play them on systems for which they were never designed. ScummVM is a complete rewrite of these games executables and is not an emulator per-say. 

ScummVM supports an extensive library of over 325 adventure games That said, you can find a full list with details on which games are supported and how well on the compatibility page.

SDL 2.0.x (or SDL 1.2.x) is a required Library.

Ruffle is a Flash Player emulator written in Rust. Ruffle runs natively on all modern operating systems as a standalone application, and on all modern browsers through the use of WebAssembly and has extensive content compatibility in ActionScript; the language that powers interactivity in games and applications made with Flash.

Users or website owners may install the web version of Ruffle and existing flash content will "just work", with no extra configuration required. It will also detect all existing Flash content and this is an entirely open source project maintained by volunteers.

This is a pseudo-driver module that intends to improve compatibility and stability in games using Direct3D8 for rendering by converting all API calls and lowlevel shaders to equivalent Direct3D9 ones. By that it also opens those games to the new possibilities from proven tools and wrappers written for Direct3D9

Steam Rom Manager is a bulk game importer and artwork manager for Steam. It's basically an app for managing ROMs and benefiting from what Steam has to provide. This includes using big picture mode, its overlay, controller management layout,  streaming options and much more..