I think Superman is the top herald pound for pound because despite not being as versatile as his peers (Surfer, Thor, Genis, Alan Scott, etc) he can still get most jobs, if not all jobs, done, through creative uses of the limited abilities he has. He does the most with the least. Surfer isn't tops pound for pound because he has almost the most, if not the most, tools at his disposal in the tier. He wouldn't have to vibrate at a certain harmonic and/or rub his hands together at multiples of C to get certain effects. He could just wave his hand or channel the power of cosmic effortlessly for the same effect. Same goes for Thor/Mjolnir or the Rings/Bands bearers. Superman, given what he has, punches the furthest out of his comparative weight class in spite of his seeming powerset limitations. That doesn't make him the top herald, but it makes him the most effective given the smaller tool box he has. He's like an Allen wrench that can somehow program a computer and perform laser surgery.