There were actual three sequels: "Return of the Seven" (1966), "Guns of the Magnificent Seven" (1969), and  "The Magnificent Seven Ride" (1972).
There was also a Italain version of "The Seven Samurai" called The Seven Magnificent Gladiators" (1983), plus a television series that lasted from 1998-2000; therefore, a video game based on the original film, would hardly seem out of place.