If you're looking for some deep cuts, here's a few. We all stand on the shoulders of giants, so present standards, some of these may be more "influential" than good.
Caesar's Godhood
http://www.bay12forums.com/smf/index.php?topic=55726.0The game that really pushed "God Game" genre on this forum back in 2010. Godhood itself would get eight games over the years, and inspire countless other games.
Iituem's Godhood V: Legacy of the Titans
http://www.bay12forums.com/smf/index.php?topic=97735.0The fifth game in the Goodhood series, was GM'd by Iituem in late 2011. He'd then go on to become a prolific GM for many years, including running some of the more (in)famous games such as Hive Race and Wands Race.
10ebbor10's Salvation : A Spaceship suggestion game
http://www.bay12forums.com/smf/index.php?topic=116652.0Again 10ebbor10 ran so many games in this period it's hard to single out 'his best', but later in 2012, 10ebbor10 began GM'ing one of his longest running games, a Sci-Fi SG. (In 2013, it got a spin-off: Wagon Train to the Stars.)
10ebbor10's The Glorious Design Bureau of the People
http://www.bay12forums.com/smf/index.php?topic=131248.0In Sep 2013, 10ebbor10 would launch a proto Arms Race. Primitive by modern AR norms, you can see so much of the DNA of the genre emerge here. Derived from "The People's Weapon Design Bureau: Нет электромагнитные пушки животны" from Spring that year, the GM put enough structure together to make a SG sandbox into an actual game.
Sensei's Arms Race
http://www.bay12forums.com/smf/index.php?topic=152099.0The first true Arms Race launched in Summer 2015. Two sides, PvP, map, resources, designs, revisions... Sensei put together the mechanics to make the genre. Given how spectacular battle reports tend to get in present AR's, its fascinating how humble the writing was back in the day.
Nirur Torir's Kaiju-COM
http://www.bay12forums.com/smf/index.php?topic=140300Nirur Torir is one of those GM's that's been around these parts for forever. Such a huge body of work over the past 10+ years, but in Summer 2014 Kaiju-COM popularized a high-effort genre that I always love following. (2019's Kaji-com 2 by Devastator was a great reboot that ran for a year and a half.)
Nuke's Demonhood 2 was already nominated, so I'll +1 that. Nuke's such a solid writer, and his AR's are always great to follow. Being an AR nerd, I'd definitely nominate him for NUKE9.13's Battle for Aljadid
http://www.bay12forums.com/smf/index.php?topic=168246.0Late 2017, AR in SPAAAAACE. Other than theming, this AR is also known for popularizing 2d4 over 1d6. Mechanically, that's something virtually all AR's do now.
Draignean's Arms Race: War of the Cinder Spires
http://www.bay12forums.com/smf/index.php?topic=164853.0You wanna know why people get excited when Draig launches a new game? Cinder Spires from Summer 2017 is why. While he was known for RTD Deviation-22, Draig setting an AR in an aetherpunk setting with fantastic writing and PvE element remains one of the most fondly recalled AR's among the community.
Sensei's Intercontinental Arms Race
http://www.bay12forums.com/smf/index.php?topic=163937.0Running for two years straight across two forums, Sensei's ICAR was the most popular and enduring AR ever made. Actually his third game in a trilogy, the first being the original AR in 2015, and the second run on Spacebattles.com. A helluva an accomplishment to spend years fully completing a series.