DGen is a free, open source and portable emulator for Sega Genesis/Mega Drive systems.
- Game Genie/Hex codes support
- PAL/NTSC, fullscreen modes
- Joypad/joystick and mouse support
- Highly configurable controls
- OpenGL textured video output
- Portable (64-bit, endian-safe)
- Screenshots, demos recording and playback
- Debugger with M68K and Z80 support
- hqx and scale2x upscaling filters
- VGM dumping
- Low CPU usage on current hardware
Maybe not the most accurate emulator, but open-source, compiles on Linux/x86-64, is still maintained, and has some great features (such as debugger or sprite boxing). It's great to see a Genesis emulator for Linux, even though it's limited to x86 and ARM architectures.