Biggest leap forward from a system to its successor

[Hiku]

Technology wise, 2D to 3D (SNES > N64) is a leap we'll likely never come close to again.

While primitive 3D to competent 3D (PS1 > PS2) was the most impressive leap within that technology for me.

NES > SNES is in that category as well.
Also because controllers evolved from having only 2 face buttons to 6.