Bruce would do better than most of you think,but a lot of people make him out to be unbeatable(no man is unbeatable) but he could fight man, Like someone said you should see him train and spar the dude was an aninmal. As for competing in todays arenas he would do ok but combat has evolved,but im sure if he was here now in his prime he would adapt and destroy(imagine if he got on the juice and slapped on 30 pounds he would still be lighting quick, you underestimate how powerfull the mind is and Bruce was the master of the mind