Melee for Nintendo GameCube is still being played after all these years because of its vibrant competitive scene.
While this is fine for some games, Super Smash Bros. Since the original console being emulated wasn’t made for online play (and netplay is a hack on top of it), what’s happening is the emulator’s “state” is constantly being synced between players. Netplay enables online play in emulators, but it isn’t quite the same as traditional online play in video games.
