Well the brain is not necessarily the most sophisticated computer around, it's more like the best processor currently around town (Earth) but not even necessarily the best model currently in the universe, or the best model for the upcoming future (I'm just nit-picking, sorry!).

Our (non-neuron) cells themselves are highly autonomous, specialized, and together form quite a powerful processing unit too (processing in the sense that they basically act on information that they receive).

Brains, I believe, are even messy processors, subject to way too many failures, exceptions, bugs. Contradiction, in general let's say, is impossible in an AMD processor ... but in our brains it's a daily event.