EmuNations

Genesis Plus GX core:

RetroArch is a frontend for libretro emulator cores, game engines and even media players. It enables you to run classic games using Libretro on a wide range of computers and consoles through its unified graphical interface. Settings are also unified so configuration can be done once and applied and applied to all. It has advanced features like shaders, netplay, rewinding, next-frame response times, and more.

It can run on the usual platforms like Windows, Mac OS X and Linux, but it stands alone in that it can support far more platforms beyond just that.

• Ludo - A smaller libretro front end by only implementing the core features and by targeting less platforms but definitely shares a lot of the same core values.

• Lakka - lightweight Linux distribution for small computers like Raspberry Pi

• RArch - It incorporates Kaillera to offer the possibility to play games online. 

Ares was originally Near/Byuu's last project and was subsequently continued by new developers (including Luke from Cxbx-r). That said, it's an open-source, multi-system emulator focusing mainly on accuracy and some of its exhaustive features include but are not limited to native multi-platform UI adaptive sync, dynamic rate control, save states, run-ahead, rewind or fast-forward and much more..!

Kega Fusion is a closed-source Sega SG-1000, SC-3000, SF-7000, Master System, Game Gear, Genesis/Mega Drive, SVP, Pico, Sega/Mega CD and 32X emulator. It's packed with features but hasn't been updated in quite a long a while.

Note: On Windows 10, an incompatibility issue causes the emulator to freeze when attempting to switch to fullscreen mode. To fix it: right-clicking on Fusion.exe > Properties > Compatibility > check "Disable Fullscreen Optimizations".

Also, DPI scaling might affect the output resolution display. You might have to adjust it in compatibility also, if the emulator window is partially-filled. 

BlastEm aims for cycle accuracy while also hitting lower system requirements than similar emulators. It has substantially higher compatibility than Exodus but falls short of Genesis Plus GX. Commercial game compatibility is close to, but not quite at, 100%. It is the only emulator other than Exodus that can properly display direct color DMA demos and to pass all of the tests in Nemesis' VDP FIFO Testing ROM.

Clownmdemu is a Sega Mega Drive (a.k.a. Sega Genesis) emulator that'sactive and looks promising with support for Motorola 68000 instruction durations, save data, Debugger and accurate window plane emulation. written in C++11 and leverages the SDL2,

It also as a Browser and libretro version...

BizHawk is a multi-platform emulator written in C# which focuses on core accuracy and power user tools. Its main features are TASVideo (Tool-Assisted Speedrunners) for full recording and debugging tools as well as Lua scripting. The consoles covered include but are not limited to Apple II, Atari 2600/7800, ColecoVision, DOS, Game Boy/Game Boy Color/Super Game Boy, MSX, Nintendo Entertainement System, Super Nintendo, Gameboy/Color, Sega Master, Sega Genesis, Sega 32X, Sega Saturn, Sega GameGear,  ZX Spectrum, Atari 2600/7800, Commodore 64 and a few more!