Twenty years ago today, the Sega Genesis was released in North America.  Known as the Mega Drive in Japan, the Genesis was a big hit.  The NES was dominant at the time, but that fabled console was a bit long in the tooth.  With the help of truly superb marketing (Sega does what Nintendon't!), and a certain blue hedgehog, the Genesis became Sega's most successful console.  It was also a great way to play co-op with a friend, with many stellar co-op games in the Genesis library.