I used to be able to play through the whole game in under thirty minutes. I can only do it on the original NES though, the keypress delay using a keyboard is too significant in that game, the timing is so tight. That game really highlights the high latency delay between a keypress on a keyboard and using a controller's D-pad if you try to use an emulator.
The first minute with Tyson is the hardest, but it is also the most predictible. The timing of when he punches is the same every time unless you counterpunch, in which case you can get in two hits for every punch of his, and he throws half as many punches in that minutes because you've stunned him. After that first minutes he adds more variety to his routine. The first time I beat him, I won by decision.
I can also get past the first five fights with just audio, and the video off.