Clan of Embers, which is currently screwed up though.
My second favourite are Mercurians.
My favorite remains the Elohim after trying out the two new civs. Maybe the poll could be refined a bit to ask for a Favorite Leader. I just love playing as Einion Logos and it is easy to get the Altar Victory with him at any game difficulty.
onedreamer, I don't want to stray too much OT from this thread, but I have to ask you about playing the Mercurians in .30. They used to be my 2nd favorite too, but I was just about to start a new thread on why they are unplayable (without a lot of grief anyway!) in .30.
The many bugs (I mentioned some in the bugs thread) combined with the horrible ally AI is just too much and I am very reluctant to build the Mercurian Gate now. I still love taking the Big Guy out with some Angels to bring down the bad element, though, I must admit.
But, haven't you seen a lot of problems when you take over as Basium?