I haven't played a huge amount of boxing games but this is the only one that has ever made me feel like I'm in the ring. Playing this with a friend will have you both sweating by the end.
The controls have been perfectly balanced so that speed fighters can dance around their opponent to stay on the outside and the counter punching mechanic allows the slower sturdier fighters to get hard shots off. You can wear down the faster fighters by working the body and you can take out a bruiser by collecting points.
The fact that you can make the choice to play in this way shows that skill over chance is what will win a fight in this game. Unlike later editions which have been oversimplified to the point that the fighter's style and stats are the most important factor. As long as you have the better stats fighter you will win.
The punches are just so satisfying. This is probably what has kept me hooked on this game for so many years.
Character creation in this game is also great fun and their faces can be pretty hilarious between rounds!