The original SNES multitap was released in 1993 by Hudson with Super Bomberman as a pack in. Hudson later released a second version along with Super Bomberman 2 that was shaped like Bomberman's head.
Over 20 additional multiplayer adapters were released by various other companies, including a few with 5 additional controller slots. Despite appearing to have support for 6 players, the 6th player slot has been shown to not be operational.
Between the SNES and the Super Famicom there are more than a hundred games that support more than two players.