I think the phrasing of this question is a bit ambiguous. Are you interested in games of historical importance to the IF community, where the game changed the course of a (still rather small, even today) community of IF creators? Or are you instead interested in really great IF games worth sharing with your listeners? Or are you interested in games that sparked a lot of community discussion?
If you’re “just” looking for great games, you’d do well to just hit up the IFDB Top 100. (Beware, this page takes a minute to load. Just be patient.) https://ifdb.tads.org/viewlist?id=k7rrytlz3wihmx2o
Many of the greatest IF games of all time, games at the very top of the IFDB Top 100, were unprecedented when they launched, and widely praised, but nobody really followed in their footsteps either. Here I’m thinking especially of some of the largest and most technically complicated works of IF, where the cost of following in their footsteps would be extremely high.
I would include these games on the list of great works that did not change the way everyone else made IF:
- Counterfeit Monkey
- Hadean Lands
- Lost Pig (specifically the way its parser could handle pretty much any crazy idea you’d throw at it, making it particularly approachable for newbies)
- Blue Lacuna (I really wish this had changed everything… its parser innovations woulda shoulda coulda made it into Inform’s standard rules)
Each one of those games could have kicked off a whole genre of games following in their footsteps (letter-remover games, auto-completing recipe games, generous-parser games), but didn’t.
By comparison, each game that did change the way we built IF was usually the game that launched an IF platform. This isn’t necessarily the platform’s first game, or even the first “real” game (as opposed to a technology demo), but, as I like to put it, the first “admirable” game for that platform, the game that made people say, “I really like this game, and I would like to make another game just like it. How did the author(s) make it?”
For those, I would point toward these:
Deep Space Drifter kicked off TADS as a platform
Curses! kicked off Inform
Encyclopedia Fuckme and the Case of the Vanishing Entree kicked off Twine as a platform (also howling dogs)
Choice of the Dragon and/or Choice of Broadsides kicked off ChoiceScript and Choice of Games (also Choice of Robots)
Sorcery! and/or 80 Days kicked off Inklewriter (and Inkle), which later became Ink (also The Banner Saga)
All of these games were well received, but IMO none of them are the very best each platform has to offer. (It would be rather depressing if the game that launched a platform was the best game anyone could ever make on that platform!)
As for kicking off discussion, I’d point to Depression Quest (one of the major flashpoints of Gamergate in 2014), howling dogs, De Baron, Photopia, Rameses, Aisle. See also the IF Theory Reader particularly “10 Years of IF: 1994-2004.”
Probably the biggest historical turns in the community’s discussion coincide with changes in the way we communicate:
- the formation of rec.arts.int-fiction and rec.games.int-fiction on Usenet in the '90s: lots of aspirations toward academic literature (e.g. “Crimes Against Mimesis”). There was a lot of reviewing, and a lot of flame wars around those reviews; because it was Usenet, it was impossible to ban trolls. Perhaps as a result of Usenet’s structure and affiliation with universities, I think there have been fewer canonical IF Theory articles written in the 20 years of the 21st century than there were during the Usenet period. By “canonical” I mean must-read articles that the whole community was familiar with. (More stuff gets written nowadays, but there’s no particular article that everyone has read; the self-described “academics” are now a much smaller portion of the community.)
- the formation of intfiction.org in 2006: It took a while to get going, but it became the central hub for IF discussions post-Usenet.
- IFDB in 2007: IFDB became the repository for IF reviews, but in the style of IMDB; these reviews were mostly not in any sort of conversation with each other, unlike the Usenet days.
- the addition of a Code of Conduct to intfiction.org in 2014: It’s not a coincidence that this was the same year as Gamergate, forcing the community to decide what it stood for, who would be welcomed, and who would be banned.
- switching from phpBB to Discourse in 2019: Discourse hugely expanded the toolkit available to moderators, including the ability for ordinary users to flag a post before moderators take action, preventing brushfires from becoming flame wars.
- the formation of IFTF in 2016: IFTF now hosts and organizes this forum (as well as the NarraScope conference, IFComp, the IF Archive, and Twine development). The community is now supported by a dedicated non-profit.