this one is a multi emulator that supports netplay, the systems it supports are these:
Atari Lynx
Neo Geo Pocket (Color)
GameBoy (Color)
GameBoy Advance
Nintendo Entertainment System
Super Nintendo Entertainment System/Super Famicom
Virtual Boy
PC Engine/TurboGrafx 16 (CD)
Sega Game Gear
Sega Genesis/Megadrive
Sega Master System
Sega Saturn (experimental, x86_64 only)
Sony PlayStation

it uses mostly usa roms, for netplay it uses various servers, which i will post here:
i'll post the simplified version of mednafen with the newest version of mednaffen, which is 1.21.3: