Xevious - The Avenger (USA) ROM

Xevious is an extremely difficult top-scrolling shooter, a very early game that established many unprecedented game elements that are now commonplace. Like many influential forerunners, Xevioius now seems outdated and frustrating if one is not aware of its place in history (see some other article for that--I am about to discuss gameplay and mostly ignore history).
It is no accident that the name of this game is one letter different from "devious." It is quite difficult due to the AI of the enemies. They tend to fill the screen with weapons aimed either right at you or right where you should normally be going. You have to be fairly sneaky to beat or dodge most of the enemies. It is easy to get into an essentially impossible situation.
Most players nowadays would expect a completely different level after finally beating the boss, but instead you will find a very similar-looking next level with smarter enemies in better formations. This game came only four years after Space Invaders, but its variety of enemies was surprising for its time. This game will have you at the edge of your seat if you intend to become an expert, but most players will become frustrated and move on to something else.