Heck, Doom's leap to 2.5d FPS was already a leap (not the first attempt at 2.5d or 3d, sure, but the one that did it quickly and visually good. (Different genres, but Alone In The Dark did full 3d rendering (voxels, not sprites) very nicely but painfully slowly, and Elite had done wireframe-3D space combat, etc, for about a decade beforehand on far more basic personal computers. For example. Wolfenstein 3D was (2+)d intermediary, of course. Never played Half Life, but the next push I recall was Quake (or diversion over into the likes of Descent/Magic Carpet, depending upon what kind of game you like... Battlezone and Battlefield were probably more my thing, with a bit of Tomb Raider and GTA3 and of course Duke Nukem to bring me back to an enhanced 2.5d sprotes'n'vectors playing environment).
Of course, some of the leaps are different quality to others. The whole Sims thing was basically little more than isometric, but looked good enough for all that. There were a few "loops and jumps" racing games (that really worked best on arcade hardware, often) that had marvellous freedom of movement but it was often little more than filled-wireframe.
But you could generally get a good single-player game, by default, due to multiplayer opportunities (even by null-modem) only being an "if you can" playing option. Later on, it looked like the single-player progression was left to fester as the big attraction was massively-multiplayer deathmatch/team-vs-team-coop feature, and the AI enemies (to swing this vaguely back to the topic) were often stupider than the previous Doom-sprite type player-hunting entities. As I gravitate to single-player stuff (I did a lot of solo Survival Mode minecraft, rather than multiplayer Cooperative/otherwise, I think I'd appreciate a good ability-scaling AIish opponent (hovering between challenging and slightly impeding, tracking my playstyle to some degree to make the personal grind interesting without any degree of hopelessness.
But, yeah, incrementals in development but I think the next leaps are going to be in aspects we can't easily anticipate (a little-known side ability gets its own revolution, or even some principle that's entirely novel).