I'm afraid you're quite wrong.
It's not a mere matter of air flow.

Besides airflow, there are two more key parameters in the transfer of heat to air: the contact area and the temperature difference between the contact area and the air.

In order to maximize heat radiation you want your heat sink to have as much contact area as possible. Thus, the heat sink designs with lots of big fins.

However, there's a catch. The material's (aluminium, copper) thermal resistance will produce a temperature gradient.
That is, the heatsink will always be hotter at the base and cooler at the edges.

This means that increasing the contact area has diminishing benefits: you increase area, but a greater part of that are is cooler and radiates less heat.

Enter water cooling.
With a circulating fluid, like water or oil, the temperature gradients are much smaller.
In turn, this allows for radically different radiator designs, with a much larger and effective contact area.