Smoothness, feeling of fluidity and responsiveness. Being very timing-sensitive and twitch-skill-based, SMB would gain a lot more from 120 Hz than a slower paced game would.
[1] Of course, the gains of going from 60 to 120 fps are much smaller compared to 30 to 60, but still. People have PCs and monitors capable of running SMB at 120 fps, so being bottlenecked by the software is frustrating.
http://www.testufo.com/#test=framerates
Smoothness, feeling of fluidity and responsiveness. Being very timing-sensitive and twitch-skill-based, SMB would gain a lot more from 120 Hz than a slower paced game would.
[1] Of course, the gains of going from 60 to 120 fps are much smaller compared to 30 to 60, but still. People have PCs and monitors capable of running SMB at 120 fps, so being bottlenecked by the software is frustrating.