You know I thought maybe I was just getting better at timing the combos in street fighter but I guess if you think about it, your given an extra frame to pull off a move. Which I guess is kind of cheating.. but I'm not playing competitively or anything. And it evens the score against the cheap CPU.
So it's not really input lag but extra input time.
It's still input lag.
1. This is because original arcade games didn't have a buffer. They scanned out the graphics in real-time to a CRT.
2. Emulated MAME adds input lag, compared to the original machine, because MAME uses a framebuffer where none originally existed.
3. Using 120Hz reduces this MAME framebuffer lag.
So you're actually getting closer to original manufactured videogame responsiveness, by reducing the MAME framebuffer lag.