Influence and popularity are inevitably intertwined — one often leads to the other. However, being the first doesn't necessarily mean being influential, since later works can refine and perfect what came before. Pong, for instance, was one of the first and still holds enormous influence and legacy in the gaming industry. But in the case of titles like Wizardry or 3D Monster Maze, unless you're a dedicated gaming historian or enthusiast, very few people are even aware of their existence.
That's why I don't quite agree with the idea that a game must predate the definition of the industry to be considered influential. If we follow that logic, then films like Arrival of a Train at La Ciotat Station or A Trip to the Moon would have to be regarded as the most influential movies of all time — which is, at best, debatable. Influence isn't just about being first; it's about shaping what comes after — the works, creators, and audiences that evolve because of it.
		
		
	 
I take your point, but popularity - at least numerically speaking - because of the way gaming has gotten exponentially bigger over the years, is always going to have a massive recency bias!
Everything has to start somewhere, and it will initially be a way smaller "scene" than what we have today, so it seems right to me that we need to go back at least to close to the beginning to judge what's proven to be the most influential.
I  chose PacMan very specifically because of how impactful it was in terms of being the original mascot character more than anything else. Now I'm not saying that every influential or important game has to be character-based, what I'm saying that its way easier and quicker to spread a character identity,  than a mechanical or experiential identity.
In many ways the many virtues of Super Mario Bros kind of prove why I came to the conclusion.
* SMB is important for all the historical business reasons people have cited already. It was the phoenix that led the industry out of the ashes of the 1983 crash, and crucially because it was a really great game that people loved and still love to this day.
* But here's the thing; how much of its historic importance is tied to the fact that this is literally the "face" of Nintendo. Its central to their marketing both as visual element and as proof of the whole "Nintendo seal of quality" schtick ? And over the long-haul has not the standard of games featuring the character been consistently higher than industry average?
* Mario's been exception well-served over the years. Its been reputationally protected, and rightfully so.
The point I'm trying to get is its important in marketing and business sense, as well as purely creative, or user-experiences aspect. The combination of these things I'd say can be fairly munged together as overall cultural impact.
The thing is, in my view under those parameters PacMan still comes out on top.
* Huge in its day across all gaming markets, not just the face of a proprietary console brand.
* Remember, gaming history is about more than just consoles. Millions of people (users and creatives alike) came into gaming from outside the console space.
* PacMan as a brand is still is world famous in spite of not being protected nearly so well, and often being attached to forgettable product.
* It was also revolutionary in establishing the idea of mascot characters, also the first attempt to reach a female audience with Ms Pac Man.
* Given its time of release it was genuinely novel as a game too. And yielded as many copyists in its time as SMB did following its release.
* Business significance is huge because its the Yin to Mario's Yang over the whole '83 crash for reasons mentioned in an earlier post.
Sorry, long post.  I've given this a lot of a thought because Its a really interesting question:  What is the most influential game of all time ?
I'll be honest and say that SMB was the first thing that popped into my head. But, after I thought again trying to be as objective as possible the answer suddenly became obvious to me.