Okay, here's a huge example that has seemed to slip past your bias -
Regardless of your personal opinions about the game either way Undertale has had one of the largest impacts on gaming as of late. The amount of penetration and inspiration in the form of art/video/animation/discussion doesn't really even have anything close from a 3D counterpart.
A game that is very primitive 2D, uses chiptune...really a game that could have been made on NES hardware almost completely.
There are so many other examples as well; like Braid, Shovel Knight, Cave Story, Ori and the Blind Forest, Limbo, Inside, Axiom Verge, Super Meat Boy, all of the modern Kirby/Yoshi/Mario/DKC 2D platformers and yarn games, Rayman Origins, Trine 2, GBA and DS Castlevanias/Metroids, Muramasa TDB, Odin Sphere, any SHMUP or fighter game, etc
The point that you've brought up twice now is pure speculation. If 3D never happened you'd be none the wiser and you'd still be playing awesome games. Even 3-4 generations now into 3D; a lot of 2D games are still being made, that's significant. Videogaming wouldn't get stagnant, the artform itself is strong enough to not need gimmicks and such. I'm not opposed to 3D where it's at now, but it sure did take a while for game makers to become competent with the medium, and for the majority of games to age well.