Tyson's whole training as a boxer is to attack with power and speed but only with fists. He blocks like a boxer and expects to take blows to the upper body in highly regulated circumstances. Tyson blocks by a guard absorbing blows.
Bruce Lee fights with fists, feet, elbows, knees etc, is more spontaneous and there are no limits to what he can target his strikes. Bruce Lee blocks by deflection.
Unless it's a boxing match with the rules that apply, Bruce Lee would have the significant advantage. Tyson would definitely have the advantage of fighting without gloves, but that's about it.
If weapons are involved, Tyson would probably pick knuckle punchers. Bruce would have lots of other... options.