If you can make it past the first round, its not too hard, but still a small challenge. If it goes to decision at the end of the 3rd round, theres (I'm guessing), an 80% chance the game will pick Tyson as the winner.
I beat it while drinking heavily one night in a friends dorm room with 7 of my buddies drinking and cheering me on. I still to this day have no idea how I did it b/c I was drunk, but I guess I was 'in the zone'. One of them talked about it for 2 weeks like it was a real accomplishment. "Man, I still cant fuckin believe you beat Mike Tysons Punch-Out! You didnt lose 1 fight and I watched you drink at least 8 to 10 beers during that shit!!" LOL.