I feel like it has this sweet spot where the games feel fast like on the NES (unlike the SNES or Genesis which can feel clunky) but are more sophisticated than the NES I’m also a big fan and really enjoy the pc-engine mini.
Mario surprisingly is actually a much faster and responsive character and the gameplay feels much better for it.
Might be noticing key frame animation in 8 bit games. It can have a really nice subtle effect.
In all honesty sonic movement is pretty good, my take is exaggerated in order to compare it to mario, a game,I feel, that plays and flows slightly better than sonic(a surprisingly slow game despite the main characters name). That being said, younger me played the hell out of both of them.