Unless you belief in a mystical soul component (I do not), there is nothing else "there" but machine. A very complex, biological machine. But there is no reason to believe that that a sufficiently powerful software/hardware can not replicate the functionality of that machine exactly. Then what possible difference could there be between the two duplicate machines?

But, we will have systems that exhibit a many aspects of "thought" and sentience long before we are able to code up homo sapien sapien.

Although, it's possible that creating something that does what humans do requires the same materials humans are made of (but seems unlikely, or at least I think other materials will allow a close approximation).

I'm with you though: consciousness and sense of "self" are just matters of complexity of the brain.