Gunstar Heroes is truely one of the greatest Genesis games to ever set its pins in my Genesis' cartridge bay.
As the Gunstars, you are tasked with deactivating the evil robot Golden Silver, who is revived by Smash Daisaku. Gunstar Green is taken hostage by Daisaku and they find the 4 gems that hold Golden Silver's power. As Blue and Red, you must run and gun your way past enemy after enemy to defeat Golden Silver.
The game plays like any other game in the genre, such as Contra. There are four different weapons in the game. Players can also throw enemies, perform a sliding attack, and jumping attacks. Gunstar Heroes has a life system like no other. There are no lives in the game, just number of times your character can get hit by an attack. At the end of this number, the player can continue, or choose to end the game.
Gunstar Heroes is a tough game. Because of its life system, the game usually reverts to a 'do not get hit but keep shooting' style of play. The boss enemies are utterly huge and have many sprites for fluid animation. The boss battles are the best part about the game. They are each unique and require a different style of attack and defense.
If you are looking for a tough game to play, or just a great game to add to your Genesis collection, Gunstar Heroes is your pick.