Games

Slay the Spire spawned a ton of deck builder roguelites.

First thing that came in to my mind was Gears of War with its specific third person view and hiding behind covers. I don't think it was the first game with that mechanic but the most influential one

Battlefield 1942 always stands out to me as the one that popularized large scale online battles on big maps with vehicles. At the time it was revolutionary in online gaming.

Command & Conquer: Renegade came out around the same time as well, with similar features. I kinda wish that game had a sequel as well.

Another gameplay feature that comes to mind is the exclamation/question mark above NPC characters for quests. I remember it first from WarCraft 3, but I think it really kicked off with World of WarCraft to get adopted by many more games.

Donkey Kong (1981) popularized having different levels in a game to progress a storyline. Until then, you would have the same level over and over with increasing difficulty

Ocarina of time, 3d, lock on, one enemy attacks at a time. So much of modern gaming pulled from ocarina of time

Though it was used in a few games before, a Quake tournament and Half Life 1 cemented the use of WASD controls.

Bullet time was popularized in max payne.

Maybe cheating a bit but there are several genres of games that are named after the games that popularized their mechanics such as roguelike/roguelite, souls-like, metroidvania

Minecraft for the fully breakable/buildable procedural open world.

The original XCOM is the source of grid based inventories.

Star Control 2 is the first RPG that did the standard dialogue interface where you talk to someone and choose from multiple replies.

Mario 64 definitely paved the way for most of the 3D platformers of the 21st century

I think Spyro was the first mainstream game to standardise achievements, you could do random stuff in-game and it gave you a little pop up, carried over to Ratchet and Clank and now every game has official achievements

Kinda wild to see nobody mention System Shock, the game that invented audio logs. It may seem quaint in retrospect, but at the time all shooters were in the vein of Doom, and story in a shooter was considered "like story in porn." System Shock was not only the first to communicate the plot and next steps to the player through found audio logs, but it also filled the player in on side stories and provided characterization to the survivors on Citadel station.

The game recently got a remaster, and despite very few gameplay changes, still holds up really well in 2024. You can really see the bones of later games in it, such as story focused shooters like Bioshock or F.E.A.R. and I'd really recommend it to anyone interested in playing a great retro game.

Batman: Arkham Asylum's free-flowing combo system was copied by many future games.

CoD and Assassin's Creed popularised selling the same fucking game 20 times

Quake revolutionized fps games

Ape Escape was the first PS1 game to require the dual shock controller

For first person shooters (mix of first introduced and popularised):

Doom: started and popularised the genre. Also started and popularised rasterized 3d graphics for gaming (though the game itself was still 2d). Also first fps multiplayer and modding

Quake: various game modes (Deathmatch, capture the flag), as well as being the first true 3d fps. Popularised multiplayer and modding.

Team fortress (quake mod): Different specialist characters.

Goldeneye 64: popularized multilayer console fps, taught character size can be a significant advantage/disadvantage, depending on if you got Oddjob or Jaws.

Half-life: started horror fps genre, (mostly) seemless world

CS: customizable loadouts instead of search for guns each time you spawn, more game modes

UT: AI bots

Perfect dark: secondary fire for weapons

Deus ex: rpg fps

Halo: finally figured out a decent controller control scheme (one stick looks, one moves, button for grenades rather than needing to select grenade from list of guns). First fps I remember vehicles in, too.

Battlefield: large scale multiplayer

Socom: fps game that isn't first person, online console multiplayer

Call of duty: using gun sights to aim

Far cry: open world fps

Doom 3: used lighting (or lack thereof) to bring fps horror to a new level.

Crisis: famous for pushing hardware and people caring more about the benchmark results than the game itself (I tried the second one, it was ok but I didn't really get into it)

Call of duty: zombies (and other alternate game modes), kill steaks, online progression (unlocking guns and attachments as you level, prestige levels)

HL2/portal: brought physics and its involvement in fps games to a new level

TF2: f2p, microtransactions (though not predatory or p2w so the game isn't remembered for this)

Borderlands: loot-based fps rpg

Metro 2033: fps survival

Halo reach: custom maps

Destiny: MMORPG FPS

Overwatch: hero-based, and hero roles (dps, tank, healer)

Pub bg: battle Royale

Which game popularised the now household mechanic of being shut down after a couple of years?

Iirc (edit - apparently incorrect) Halo was the first to use left joystick as forward/backward and left/right strafe; and right joystick as look up/down and pivot left/right.

I even recall articles counting it as a point against the game due to its 'awkward controls' ...but apparently after a tiny learning curve, the entire community/industry got on board.

The first RTS is an obscure Japanese game called Herzog Zwei,

Westwood studios then made Dune 2 and Command & Conquer which basically polished and popularised the genre for the rest of the world.

Pretty much every RTS that followed took at least some inspiration from how those games worked

Rogue for the rogue mechanic. Progressing in a game as far as you can until you die, then using some form of enhancement mechanic be harder faster better or stronger to go again.

Assassin’s Creed and the Open World Gameplay design. It definitely existed before then, but after AC came out, it felt like every RPG switched to the open world map.

I don’t know what game first came up with it, but Super Mario RPG was the first time I saw timed hits for attack and defense in a JRPG. While the mechanic isn’t exactly ubiquitous it has popped up in a handful of other games over the years and it always reminds me of that game.

Spacewar! was a F2P PvP game with no microtransactions and no battle pass. Although it's hard to quantify exact player numbers (it precedes Steam charts), for a while it was the most played videogame in the world.

Its real-time graphics and multiplayer combat were very influential, and widely copied by many other games.

Jurassic Park: Trespasser invented physics engines in fps games as we know it. The game itself was a buggy mess and a financial disaster. The player's health was shown on the main character's boob for some damn reason. However, they did have the basics of a very good physics engine, and Valve took a lot of their ideas and incorporated it into Half Life 2.

Pacman was the first to simulate a real life mechanic, of munching pills, listening to repetitive music, and running from multicoloured ghosts.

Gears: cover shooter

Prince of Persia: realistic animations with weight. also popularized a platformer subgenre, which was called cinematic platformer but unfortunately the life of the subgenre was cut short due to the advent of 3d.

Diablo: ARPG genre, and even more so loot rarity system (especially the four tiers common/rare/epic/legendary) and affixes in loot as well.

Half-Life: a lot of good things, sure, as pointed out by other comments, but I will also never forgive valve for popularizing the game not fucking starting for ages.

Rogue and maybe more so Nethack: roguelike mechanics.

some really obvious ones are Tetris: falling block puzzles and Sokoban: pushing block puzzles.

also now pretty much obsolete but Overwatch: loot boxes. they existed before, but Overwatch made them an industry standard.