It’s probably not controversial to say that the Dungeons & Dragons game from 1974 was the most important and influential game in the whole genealogy of all RPGs. Every game that followed was either an attempt to make a game that improves on D&D or make a game that is different from D&D. They were either a direct response to D&D, or expanded on a game system that was.
The real question is, what other games can be considered hugely influential on how people design game systems today?
Traveller and Apocalypse World would be my two top picks.
In my very own opinion the RPGs can be crudely divided into 5 or six generations or stages (with a lot of overlap and finicky stuff) depending on some “development” or “evolution” in rules sets and gaming styles.
- The first and foremost is of course D&D that kind of set the scene and more or less created the hobby. There may be others that had the same idea, but this one was the one who gained traction. I would characterize this system as one with Levels and most character development happening after game starts. Fast up, easy to to handle character getting better. (Although Rolemaster belongs to that generation too and makes nothing easy).
- The second generation happened almost directly after with Runequest and Traveller as surviving examples. Level is removed and there is some work on the character before play, Traveller even removes most of the character development after game starts (which is to me the apparent reason the game never have expanded outside a very fanatic core (I include myself in that core). Characters is still generated randomly with dice rolls etc.
- After some lull the third generation comes around with GURPS and HERO (Champion) as giants, here you have absolute control of the character generation and the game is no longer fixed to a specific franchise. The players of these games are less often first timers and newbies as much as veterans longing for freedom and exploring new worlds of variants and exotica.
- Here comes the (in my opinion biggest change since the first generation) and that is the Storyteller system, what was so impactful was not so much the system, as the defocus from the system and instead started to looking at the generation of a story together (but still under the eye of a gamemaster, eh, Storyteller). The dots on your character sheet was just one part of the character, the prelude and the relations with NPC as well as PC was as (if not more) important. Character development was not any longer limited to increasing number on your stat, your relationship to the world and your role and place was more important. Sure, you have 5 dots in potence, but that don’t matter when the Prince hates you.
- (and perhaps 6) here things starts to get a bit muddled, but I think that the things that came out of The Forge with Fate and PbtA as cases in point, with the game throwing of the chains of fixed attributes (Fate) and redefining the gamemaster (PbtA) as two clear examples of what changed.
… ehe, slightly more than two cents of opinions …
If we talk about introducing people to RPGs in general, it’s hard to beat Call of Cthulhu. IIRC in Japan it’s more popular than D&D and this has spilled over into China. The top three RPGs in China are D&D, Call of Cthulhu, and Fate and in a surprising number of cases game peripherals (like dice, dice towers, dice trays, GM screens, etc.) are sold as aids for Call of Cthulhu on Taobao, the country’s premiere online shopping system.