Based on my initial criteria, there are a LOT of games that make it into consideration. I want some way of organizing them sensibly, so that I can explain not just what games make the list, but why. To that end, I’ve got the following categories, to help me filter games:

1. Enduring Classics
2. Medium Changers
3. Genre Pinnacles
4. Right Place, Right Time
5. Honorable Mentions
6. Why Didn’t I Include…

The first four cover games that I think make the cut for “best games of all time”, the latter two are for things that are close, or aren’t eligible for inclusion for one reason or another. I’ll be doing each one, day by day.

Today it’s the games that I call “Right Place, Right Time”. These games were released in such a way, at a particular point in the medium’s history, that they’ve left an unmistakable mark. Some of them, released slightly later, may not have made this list, others probably still would have, but they’re all most notable not necessarily for doing what no one else had thought of, but for doing it in the right way at the right time to make a huge splash. The biggest one of these will be no surprise:

Half-Life

First-person shooters had stories and puzzles before Half-Life. Modding games was a thing with its own community before Half-Life. These weren’t necessarily new concepts when Half-Life was launched, but Half-Life propelled them into the forefront. The wide spread of Duke Nukem 3D, Doom, and Quake mods paled in the face of the total conversions that Half-Life enabled. Counter-Strike, a hugely significant game likely worthy of inclusion in this list in its own right, started life as a mod for Half-Life. Making, acquiring, and using mods became highly accessible as the Internet spun up, and the impact of Half-Life on virtually every part of PC gaming is undeniable.

Furthermore, Half-Life introduced the concept of the active cutscene, where instead of taking you out of the game into a pre-rendered sequence, the game would simply have things happen that you could see but not necessarily reach, and allow you to keep full control of your character. The game is littered with these, big and small, including an extremely memorable opening credits sequence involving you, as Gordon Freeman, heading into Black Mesa for your first day of work. This kind of storytelling device is so common now it’s hard to imagine that it had even needed to be “invented”, yet it’s largely thanks to Half-Life that we see it in so many places.

Halo: Combat Evolved

Speaking of hugely influential shooters, it’s very difficult to talk about FPSes without referring to Halo. Prior to Halo, FPSes tended to have trickles of enemies, small numbers in small rooms slowly whittling away at your health, and obvious tells for boss fights coming right after a room full of health and other powerups. It gave the genre a somewhat predictable cadence, and you often knew what to expect. Halo changed the face of encounter design hugely, pulling regenerative shields from earlier games and putting them to use as a “breather” mechanic. Now, rather than a trickle, every encounter could be a challenging and satisfying fight for your life, and bosses could be true surprises. By limiting the weapons you could carry, Halo diversified its encounters even more, simply by continually altering the tools you had to approach them.

On top of this, Halo was one of the first big console multiplayer games, and the first to leave an indelible mark on console gaming culture. With Halo, multiplayer console gaming could go beyond the living room, offering a spectrum of opponents far more varied than one could necessarily get locally.

Call of Duty: Modern Warfare

Continuing in the line of significant first-person shooters, the next major shooter to leave a huge mark was Modern Warfare. Shortly after Halo, shooters became dominated by a slew of WW2-era games, playing out the same battles in the same locations with the same groups repeatedly, remaining popular enough to keep generating sequels but never quite standing out. Modern Warfare changed a lot of that, moving into the near-future and making the conflict more real and present, and much less abstract than the WW2 games had become for the majority of their players, nearly all of whom were too young to see WW2 as much more than an abstract concept.

Modern Warfare offered a surprising amount of variety in its campaign, which had a strong story and a lot of high-quality moments liberaly spread throughout. It provided a narrative in a military shooter beyond “win this war”, and added depth and nuance that hadn’t been seen previously. It has one of the most powerful single moments in game storytelling, and does it with virtually no words.

Chrono Trigger

From shooters to RPGs. Chrono Trigger is a classic, and a superb game in its own right, but it’s immensely notable for the huge variety of things it introduced to the genre, and games in general. It provided narrative and mechanical firsts like its selection of unique, interesting characters and the ability for your party composition to enable combos and other powerful moves, as well as previously-unknown concepts like non-random encounters that took place in the actual parts of the game you were in, no screen transition, nothing.

However, what really sets Chrono Trigger apart are its big ideas. Other games had multiple endings before Chrono Trigger, but they were relatively unimportant, and rarely represented a different path to beating the game. Chrono Trigger allowed you to beat the game in a huge variety of ways, at a surprising variety of times, and all of these would cause the game to play out differently, and not all of them were nice. You could “beat” Chrono Trigger and not feel like you’d won. Furthermore, Chrono Trigger allowed you to go back and try again, with New Game Plus, where you could take what you’d learned and some of the spoils of your adventures into a new game, hoping to do better this time. NG+ is now a staple in RPGs and many other games, and it all started with Chrono Trigger.

Final Fantasy VII

Time for me to start a fight. Final Fantasy VII is the only Final Fantasy game to make this list. Many other FF games are excellent, but none are as hugely influential as Final Fantasy VII. As the series’ foray into 3D, and absolutely gorgeous at the time, one of the best villains in video games, and a cast of memorable, complex characters, not to mention a game world that suggests it’s much bigger than what you see in the game itself (reinforced by the game’s variety of spinoffs, all telling stories of different parts of that world), Final Fantasy 7 is an incredibly significant game.

Furthermore, it pushed JRPGs into 3D in a big way, one of the first significant moves forward for a very static genre, and quite possibly the only notable one of that generation. It brought a lot of players into the genre who hadn’t seen it before and weren’t wowed by 16-bit sprites, and made a lot of games relevant that otherwise might well have vanished into the ether during the early days of 3D. While other RPGs may have appeared instead of FF7, given time, its release was timely and extremely important, bringing a gorgeous, complex RPG into the public eye right as games started to go more mainstream and draw more people’s attention.

Everquest

World of Warcraft is the game that locked down and defined the MMO genre. Everquest is the MMO that taught us how awesome MMO worlds could really be. Everquest was a social game, one of the first of its kind, where you couldn’t succeed without help and you could get just as far by knowing people in the game as knowing things about the game. Everquest was a huge, expansive world that was extremely dangerous and, by today’s standards, incredibly punitive. These things together made it a place where, by and large, players hated the world, and pushed back against it, rather than hating each other and pushing each other around over an easy world.

It was possible to meet new people every time you logged into Everquest, because the really big guilds and the clique-mentality of smaller guilds hadn’t fully formed yet. Everquest was a fiercely social game in an era when games (and gamers) were criticized for being antisocial, and it gave rise to friendships and meetings that could previously never have happened.

Mass Effect (series)

For a long time, the Action-RPG was an awkward cousin to the more standard RPGs. Real-time combat with the endless numbers of possible options simply wasn’t possible or feasible, and games tended towards “more spells and more attacks” rather than individually more interesting ones. Action-RPGs tended to be simpler, and less involved than their more established counterparts, and outside of Zelda games and Elder Scrolls, often not very good.

Mass Effect carved a niche out by blending RPG mechanics and shooter mechanics, launching a more “hard” sci-fi space RPG at a time when swords-and-sorcery made up the overwhelming majority of RPGs. It brought dialogue forward from a single “right” answer and several incorrect/informational choices, and saved a ton of what you’d done from game to game. Most of these things had appeared individually before Mass Effect, but the ME series was the first to bring them all together in a coherent, fully functional and complete way. It offered polish and high production values, and while none of the games in the series are individually quite ‘there’ for this list, the series as a whole deserves a mention.

Assassin’s Creed II

Most game series make this list as a whole group. Assassin’s Creed II stands on its own. Its predecessor was promising, but somewhat repetitive and tech-demo-feeling; AC2 was an amazing jump forward, and set up plots, metaplots, game mechanics, and characters that the series would struggle to make as compelling in later games as they were in AC2. The game delivered on the promises of its predecessor and set up the edges of a fascinating world. Stealth was interesting, and different from the light/dark systems used previously. Whereas the first only asked you to stealth occasionally, AC2 introduced more and more enemies who could simply overwhelm you, a staple for stealth games. AC2 is still a largely “stealth-lite” game, but it has enough varied systems and interesting mechanics from the first to really earn a spot, and while it didn’t invent the concept of parkour gameplay, it perfected it in a way that its predecessor and its contemporaries never quite managed.