Adventure (Atari 2600, 1978)

It was exceptionally rare to have a game on the Atari 2600 that could actually by completed.  Almost every game was endless, with a focus on getting a high score, rather than having a quest with an ending.  The technically superior arcade games were like this, so games on the 2600 sought to emulate them.  The couple games that did have endings included Raiders of the Lost Arc, ET, Mountain King, and this game from the 2600's earliest lineup, Adventure.
The story is as basic as it gets.  You are some kind of adventurer, and your chalice (possibly the Holy Grail) has been taken from you by the dragons of the world, hid it away in their black castle.  To get it back, you must navigate your way through mazes, solve puzzles, and slay many dragons.  This game has three difficulty settings.  The easiest is fairly short and simple to win with only one maze to navigate through and the resources fairly easy to find.  The second has two caves, two mazes, and the bat, who will relocate objects throughout the game.  The third level is like the second, but with every object places randomly in the maze.
Games on the 2600 required a huge amount of imagination to make its rudimentary graphics resemble what they are meant to.  The sprite you control is a square.  A sword looks more like an arrow.  Keys barely look like keys.  a blue maze makes me instinctively think of water, and my assumption is validated by a bridge (shaped like a pair of brackets ] [ ).  The bare-bones presentation must be excused to enjoy the game, and is in fact, one of its charms.  This holds especially true for early 2600 games, which came out long before Activision would make some of the best looking games for the system.
The graphics were a necessary sacrifice to fit the gameplay into the cartridge's memory.  Your only actions are to move, pick up items and drop them with the button.  To slay a dragon, you only have to touch the sword to it.  There is a surprising level of strategy that subtly comes into play with this simple play mechanic. If I want to go into the black castle with the black key, should I go back and find the sword before I progress?  Where do I place the bridge to go forward, or even create shortcuts?  Is there any way for me to use the bat to my advantage?
Adventure has grown a kind of charm that comes purely from its technical limitations.  This game was programmed by one man, Warren Robinett, in a time when Atari did not allow its programmers and designers to have a credit anywhere in the game.  Robinett found a brilliant way to sneak around this.  He made a hidden room in the game, accessible by cryptic means, which holds the credit "created by Warren Robinett," also the first easter egg in gaming.  We may now credit this man for taking the first bold steps to what would become modern video gaming.