I didn't vote, because I think chosing the civilisation I prefer is impossible, I prefer several civilisations (Luchuirps, Lanuns, Balseraphs, Clan of Embers).
And because this is a complex question, it needs an itemized answer.
The Bannors are funny to play fanaticism, spreading their religion (Order, Veil and Overlords are the best with Bannor) with diplomacy or with weapons. And the crusade is useful to declare holy war to these unfaithful sons of demon... or to resist them invading our holy land of the True Religion, and Gard promotion is original.
The Malakims have a good flavour : people of desert, son of the dunes, warriors of the sun, some kind of Fremen, etc. But they miss one big important thing to be something else than a good idea : ability to really exploit deserts.
The Eholims are nice. Nothing wonderful, but they are the best civilization for the first FfH game : defender trait for kingdom defense, spiritual trait for religion. And if your neighbor are Infernal, or Veil adepts, they become powerful (especially with the Order).
The Luchuirps... haaa the Luchuirps ! I love them
Their golem army is unique, there are so many units unaivable, so there is not any civilisations like this, so particular, so unique, so... well so good. And they are dwarf, so one more exotic touch.
The Kuriotates are wondeful too. Personnaly, I don't like them, but not for the flavour or any objective reasons. I don't like them because I like to have a great number of cities. But on a small map, I love to play with this civ and its incredible cities.
The Ljosalfars... well, I won't be objective once more. They are elves, so I give a point for exotism. They can build in forest, this is terrible. No siege weapon, a lot of custom units, again one good thing.
But these guys are the only civ who can use Ancient Forest !!! This is favouritism ! It's make me so disapointed that I never use the Fellowship when I play with them, I prefer OO or Runes.
And they are the only civ which can exploit original tiles (I mean tile you can't exploit in vanilla Civ or in a different way) !! Favouritism again !!
While they will be so close of FoL religion and be the only one to create special improvement, I will hate them. Without these two bad points, I'd love them
The Khazads have the same problem, but in a lesser proportion. 90% of people convert to Runes when playing this civ... Very sad situation, they are cool with others religions too.
But the vault strategy is different and very fun to play, their siege weapons amazing, their earth druid are really fun (I dream of druids for each magic sphere) and their unaivable unit give them a good flavor. Maybe just missing more hill and peak exploitation (like hill farm, peak mine or better workshop).
The Lanuns is one of my favourite civs. Sea civilisation, the only civ who can have a good town on a 1x1 tile island, roaming accross the sea, being the terror of the oceans, the king of sea raid, of just a peaceful civilisation of fisher. And the new ships, and navy options, are a very good thing for them. Maybe missing more sea resources, and a little more exploitation of the sea (special tile, sea improvement, etc.).
The Grigoris are cool. Not for adventurers power, because I don't like a civ for power. I like Grigori for the concepts : no gods and heros you can custom.
The Hippus are fun are very flavor too. Horse exploration, horse war, horse colonization, the civilisation of speed, the kings of razzia, the guys who visit all the pangea continent in less than 20 turns
The Amurites is not a favourite civs of mine, but I have to say they are really the civilisation of magery. Your adepts can become mages 1 turn after their production, these guys live for and by the mana.
The Doviellos are nice to play barbarian, but, like the other weather specific civs, they're missing the capacity to exploit tundra and snow tile :/
The Balseraphs... my true love
I love pacific domination, so I love culture war, so I love them
Even if I don't like the insane trait (don't like chance in game), I think it's a good idea.
The Clan of Embers is my favourite bellicose civilisation. The best way to raze cities, burning land, destroying civilisation, being the real reincarnation of Attila
And all their special units (special by stats and graphics) are a very good thing.
The Calabims have a very nice flavor, nice unit and a strategy based on highly populated towns, but I think the festen ability is too powerful : it's really easy to give 600 XP and all promotions to Losha and great vampires.
The Sheaims... well... I consider them like an unplayable civilisation... I like the spirit of this civ, but there is nothing in it, less than Infernal, so...
Just an idea about this civ : why not making them being the jungle civilization, exploiting jungles like elves exploit forest ?