The first matter of importance when it comes to discussing Lunar Lander is that it's really not such a great game. It comes from a time when technology was still ahead of design - we had the ability to create games, but no real concept of what games to create. Lunar Lander is the product of that wonderful era of exploration, though not a particularly successful one.
That said, the development of this title is incredibly significant when looking at the history of arcade games. The concept had been around for quite some time, though mostly in the form of a turn-based text adventure/mathematical equation routine used by bored engineering students who had access to thousands of pounds worth of misused computer equipment.
This maths answer without a question evolved into Atari's first foray into vector graphics and involved players using the custom control system (a couple of paddles and a strange analogue thrust control mechanism) to land a lunar module on our desolate satellite in a rough approximation of the moon landings faked by the USA 10 years earlier. Unfortunately, the latter end of the Lunar Lander coin-op production schedule clashed with the massive success of Atari's second vector based game, Asteroids.
Coupled with quite literal teething problems (the spring loaded "abort" level was just the right height and tension to knock the teeth from the head's of younger/shorter gamers), production of Lunar Lander was permanently put on hold so the cabinets could be used to house Asteroids games.
Despite the mediocre gameplay of Lunar Lander, its fascinating history and limited availability has made it one of the most collectable and sought after coin-ops of all time. Not only that, but the 200 or so unique Asteroid machines that were retrofitted into Lunar Lander cabs are even more valuable, making this a vital and alluring piece of arcade history.