On what basis? Are you assuming a transistor per neuron? If so, I would suggest you are off by a few orders of magnitude.
I don't think we have a firm understanding of what neurons do, and we certainly don't have a clear understanding of glial cells and neurotransmitters. We haven't modeled the mind of the planaria, a mere few hundred cells.
Tortoise can asnswer this far better than I.
Organic wetware (the human mind) and computer software differ in one very basic way, and I've never seen this difference considered in discussions of this nature.
Simply put, wetware is unstable. It forgets. It leaks information, relationships, meanings, inferences, frameworks, contexts and sanity. Circuit elements (neurons) die and new elements are created continuously. This is a tremendous advantage(!) that software can only partially emulate.
Wetware can fantasize, create mental structures that are impossible, irrational, and just plain stupid, and from places that a machine would never go, make intuitive leaps back into reality.
Silicon complexity and organic complexity are two different things...