Street Fighter 2 popularized and pretty much set to stone what a tournament fighter game should be. Mortal Kombat came first, but its single-player progression was this weird “tower” with some gimmick fights thrown in, like you vs 2.

Thinking about it, I’d say Mortal Kombat popularized the “REALLY fucking cheap sub boss/final boss” that many other fighting games have (looking at you, SNK) - I mean, good luck getting close to Goro in the first place.

I wonder which korean mmo could be considered as the one that de facto popularized pay-to-win as an integral mechanic.

Diablo hands down popularized not only the action RPG genre, but also having enemies as loot mystery boxes. One lucky kill and you could get your hands on a really great piece of equipment. The amount of clones speaks for itself.

I think Gran Turismo popularized the “carreer mode” of racing games.