What system was the biggest improvement over its predecessor (in overall quality, not graphics) and why?

[curl-6]

BonfiresDown said:

N64 to Gamecube. I cannot emphasize enough what a relief it was to go from blurry unstable sub-30 fps and a controller that I didn’t care much for, to a solid 30/60 fps with (comparatively) razor sharp visuals. I know you said to ignore hardware power but I consider these things to be integral to the experience.

GB to GBA. There were a few cool games on the original GB, but GBA has such a greater library. GB Color was nice, but it never really had time to get going.

Visuals can be a factor I suppose, I just wanted to be clear that the question isn't "biggest graphical leap".