I realised this last weekend, when I played it for the first time in, y'know, forever. I think, like all of us, I'd been taking Space Invaders for granted for far too long. Its ubiquity as the spark which ignited the Golden Age of Gaming has overshadowed what a work of genius the game actually is.
Yes, it was a whole bundle of firsts, and it's important in all manner of ways, but there's a reason why it's Space Invaders and not, say, Gun Fight, that has endured. And that reason is this reason: like The Beatles, or The Sex Pistols, or Star Wars, or the iPhone... it was in and of itself brilliant; not just for the time, but for all time.
I've played so many old games that I remember fondly, and now I sort of come to expect them to be broken, straining at the restrictions of the hardware, or glitchy, or trying too hard to experiment, or just damned impossible.
Space Invaders, much to my surprise, isn't like that; it works as well now as it did then.
I don't remember when I first saw a Space Invaders machine. I can recall having it for our Atari 2600. I clearly remember my mother attempting to play it - and leaning her entire body left and right as she moved the joystick - but I don't remember that moment when it first became embedded in my mind. It feels as if has always been a part of our culture.
I mean, I recall seeing it in arcades and on TV, because it was everywhere. The black and white original, the version with the coloured overlay, the one with the moonscape backdrop, the cocktail cabinet version. Space Invaders was just so utterly omnipresent in the late-70s and early-80s that it was impossible to avoid.
The artwork on the cabinet always stood out to me, because the monsters on it looked nothing like the ones in the game... and I liked the ones in the game, so could never understand why they didn't use those. And yet, that cabinet artwork, in its own way, also became iconic.
Space Invaders is, of course, considered to be the tipping point for gaming. There had been games before it - Space War, Breakout, Pong - but Invaders is the one which transformed gaming from being a niche, novelty, sideshow to bona fide global industry. The subsequent Atari 2600 home interpretation was the killer app which turned Atari into a world-conquering brand (for a while at least), and the design of the Invaders themselves has since become a shorthand for video games.
However, I think it's fair to say that these days we dismiss it, wrongly, as simplistic, a faltering, necessary, first step. We've forgotten that it didn't become a phenomenon because it was the first... but because it was genuinely great.
Playing Space Invaders at the weekend, I was suddenly struck by how perfect it is. It's incredibly well balanced, simple to understand and play, yet difficult to master. It's a game that anyone can play. Graphically and sonically it may be basic, but that simplicity is precisely why it has sustained.
That restraint and purity is something which has been lost. There have been many Space Invaders sequels and spin-offs, but none of them managed to recapture that magic. Indeed, pick almost any video game released in the last 40 years, and you can probably find Space Invaders' DNA in there - but buried by decades' worth of evolution, experimentation, and one-up-manship.
The "noisier" games get, the harder it is to identify the spine binding them together. The more games have become sprawling, map-mopping, epics, with blockbuster visuals, the less easy they are to grasp.
There's an old adage about the best songs being the ones you can strip down to play on an acoustic guitar... It's hard to think what the "unplugged" versions of Far Cry, or GTA, or Assassin's Creed would be - because they're almost an entire arcade in one, compilations of differing playing styles and mini games, strung together by setting and story.
Space Invaders, admittedly due to the limitations of the technology, never lost sight of what it was, never deviated from its core gameplay mechanic. There's something beautifully democratic in there; nobody is left behind. It starts easy, so everyone can be a part of it.
Space Invaders' creator, Tomohiro Nishikado - who not only had to create the game, but the custom hardware upon which it played - took his initial inspiration from the classic Breakout.
He hit upon the idea of making the ball a weapon, and the bricks targets... and - for the first time - having the targets fight back. His employers, Taito, forbade him from making the enemies human, so he instead tried to make them into aeroplanes... but struggled to animate them smoothly.
Depending on which version of the story you choose to believe, the decision to go with aliens was either inspired by War Of The Worlds, a magazine article about Star Wars, or a dream he had in which a group of children waiting to meet Father Christmas were attacked by space monsters.
The number of firsts in Space Invaders is immeasurable, but one of its greatest contributions to the fundamentals of gaming was the option to save a player's score on a high score table.
It was also responsible for the first e-sports gaming event - a Space Invaders Tournament, attended by 10,000 guests - and the first tabloid video game scare stories; the media ran with nonsense about students bunking off school to play it, and others suffering from "Space Invaders Elbow". In the UK, a Labour MP even drafted a bill to restrict the sale of the game due to its addictive qualities, which - he claimed - promoted "deviancy". The unmistakable four-note looping music was heard in hit singles, and even became part of the late-70s disco craze.
The game made billions for Taito and Midway, inspired the likes of Shigeru Miyamoto to become a games designer, and spawned countless - more colourful - clones, which arguably lacked the same clarity as their inspiration. Its success opened a path away from basic sports simulations to more fantastical settings.
Because of Space Invaders, the potential of gaming was suddenly limitless. That's a given. What remains a surprise is how it still holds up today.