Apples to oranges. Gate count indicates nothing when the architectures are nothing alike.

Brain is a spiking network with mutable connectivity, mostly asynchronous. Only the active path is spending energy at a single moment in time, and "compute" is tightly coupled with memory to the point of being indistinguishable. No need to move data anywhere.

In contrast, GPUs/TPUs are clocked and run fully connected networks, they have to iterate over humongous data arrays every time. Memory is decoupled from compute due to the semiconductor process differences between the two. As a result, they waste a huge amount of energy just moving data back and forth.

Fundamental advancements in SNNs are also required, it's not just about the transistors.