Not true:
SNES to PSX: polygons, textures, FMV, lighting, environment mapping, pong/goraud shading, blur, skeletal animation.
Example: Ridge Racer, Tekken, Motor Toon, Virtua Fighter, Total Eclipse, Need for Speed.
PSX to PS2/XBOX: huge improve of poligons up to 70times, online, some material effects, cube environment mapping, basic shaders, bump/normal mapping, bloom
Example: Ridge Racer V, Tekken TT,
Azurik, Wrecless, Rogue Squadron
PS2 to PS3: hires, polygon boost, precompute global illumination, particles (fog, voxel clouds), unified shaders, parallax (occlusion) mapping, AO, SSS, physics, dinamica shadows, shadow maps, etc
Example: Perfect Dark, Lair, Warhawk, PGR,
Things changed a bit with the previous gen:
PS3 to PS4: materials done right (skin, hair, leather, glass, tooth, etc), GI, improved physics and AI.
Examples: Killzone, Knack, Battlefield 3, Forza, Ryse