Gunstar Heroes is a classic run-and-gun shooter, published initially on the Megadrive/Genesis by Sega in 1993. It was the debut game of the famous Japanese developer, Treasure.
Gunstar Heroes can be played either single-player or two-player simultaneous and is generally a blast-fest through seven different stages, the first four of which you can choose to start on.
The stages vary in gameplay styles. Most are the usual left to right scrolling platform shooter style, but some are mine cart rides, or helicopter shooter sections, and even a board game. Of course: there are many boss battles, and the bosses in Gunstar Heroes are very imaginative.
Gunstar Heroes firmly put Treasure on the map back in 1993, and from this game they grew into one of the most respected developers in the world.