Was about to mention GalCiv2 as well. Stellar AI. I once read a blog post by Brad Wardell (of Stardock) where he mentioned he only added gameplay features once

Was about to mention GalCiv2 as well. Stellar AI. I once read a blog post by Brad Wardell (of Stardock) where he mentioned he only added gameplay features once he thought through how the AI can use them properly. Also, if you're tired of the more mainstream turn based strategy games, I'd recommend something like Hearts of Iron 3 or Europa Universalis 3.