It really depends on degree. Everything builds on itself. Even relatively things people can agree on as game changers build on previous experimentation. For example, Pirates, perhaps the definition of a game changing attraction largely builds on the kind of storytelling present in the disney world's fair attractions.
In terms of stuff that permanently affected how attractions were developed in the future...
The original disneyland, which shaped the basic format of most theme parks that came after.
Matterhorn, which affected coaster design everywhere from then on.
The tiki room, which debuted the major use of animatronics as the main subject of an attraction. (Really I'd group it as a part of a trinity with Carousel of Progess and Lincoln)
Pirates/New Orleans Square as being the first examples of a fully immersive dark ride (with maybe the exception of the Ford Pavillion) and the first example of a fully immersive land devoted to a single theme/location complete with merchandise and food - a format that largely remained unused in favor of almagation lands until Potter decades later.
Adventure through inner space, for inventing the omnimover which specifically for Disney was used numerous times afterwards including most of the original epcot attractions.
Thunder Mountain as the first example of a non-experiential story for a ride and the introduction of the "something goes wrong" cliche.
Disney World, for introducing the idea of a multi-park destination resort.
Star Tours, specifically for Disney introducing the use of outside IP.
Really any of the original epcot future world attractions for basically inventing the documentary style attraction (again some precedent from worlds fairs, but first major application). Really raising the bar in terms of length of experience, and scope a ride could create. Arguably not game changing though as with the exception of the great movie ride this approach has largely been abandoned in favor of Indy-style rides.
Indy for the introduction of simulator/tracked ride systems and making the rider an active participant (in a non coaster attraction) basically setting the modern expectations for ride length, thrill, story structure, and such. Tower of terror can be included here being developed roughly at the same time and with similar influence.
Shout to the original Universal Orlando attractions for collectively pushing the boundary of extreme complexity in scale and sophistication of rides and effects - particularly technologically - something that Universal still largely leads at.
Disney Sea for just blowing the lid off the level of detail and immersion expected of a theme park. Its influence is felt today in the proliferation of the modern IP based lands and in the philosophies of imagineers like Joe Rohde who breath authenticity and story as sacred.
Wizarding World - for reintroducing the Idea of a specifically themed land in all facets, and setting the precedent of what a theme park expansion and land should look like for the 21st century.
There's surely some I'm forgetting but these are the major ones I can think of that specially had a long term influence, not necessarily just what might have been a huge accomplishment. And everything again builds on what already exists so you can always trace the accomplishment back further
