A new project that has caught our attention a lot is EmuVR, a classic game emulator compatible with MAME thanks to the use of Libretro libraries. At the moment its author has it working in Unity but hopes to port it to Unreal Engine 4, with which it can become the most versatile retro platform available in virtual reality.
It is currently compatible with SNES, Arcade, PlayStation, NES, Game Boy/Color, Game Boy Advance, Sega Genesis, Sega CD, Sega 32x, Master System, Game Gear, PC Engine, Neo-Geo Pocket, Virtual Boy, Atari 2600, Atari Lynx, WonderSwan and Nintendo DS, but future plans include platforms such as DOSBox, Nintendo 64, ScummVR, PSP and Sega Saturn.
The creator is looking for an artist who wants to collaborate selflessly (it is a free project for which nothing will be charged) to carry out the project, you have more information in this thread of the Oculus forums.