Favorite and least favorite AI?

Most Liked:

Washington: A good ally to have unless you're the biggest warmonger on the map he will always stick with you and defend you.

Augustus: Don't like him because he's friendly (he really isnt) I like him cause he's a good adversary. He's one of the only AIs who can stay consistent all game especially with Military. People like Genghis and Attila seem to trail off around industrial.

Theodora: Always nice and never attacks.

Napolean: He's usually a good ally to me if you keep yourself strong.



Most Hated:

Ramkhamhaeng: The troll face acts just like he does in all Marbozirs videos.

Elizabeth: Always backstabs, never gives fair trade deals.

Shaka: annoying city spam I wouldn't mind him if I always didn't start near him.

Wu Zetain: Never become friendly and is too stubborn.


Neutral:

Genghis: Good ally to have but he shoots himself in the foot every game for. Taking city states early this is why he can never do good. Usually don't like becoming friends and ruining rep with others. If I find him later on a different continent though I usually become friends.

Favourite: Shaka and Attila. So many games I was saved by these 02 guys. You can easily bribe them to wage war on your neighbor when you feel threantened.

Least favourite: Alexander the Moron, Napoleon and Caesar. I have never had any good experience with any of these three morons as neighbor. Maintaining good relation with them is useless since they will attack you in any case, especially when you are playing on immortal/deity since your army is often smaller than them.

Regarding Genghis, he really is very friendly, but the problem is that he keeps attacking city-states! It got to the point where he was attacking city-states I was allied to, while still remaining friendly to me. I didn't really want to go to war with him, since he was just too friendly and I was already disliked by most other civs in the game (despite the fact that I did them all a favor by taking Alex out). So I found myself just placing my units on every hex surrounding a CS so that Genghis couldn't capture it without me having to bring the hammer down on him. And I found myself bribing him (a lot) to make peace with city-states.

A good candidate for least favorite really has to be the aforementioned Alexander the Jerkass. He actually contacts you just to taunt you. A guy like that can't be expected to live long...

For me..

Allies :

Genghis Khan (Mongol)- he is friendly, well, denounced me once after taking Isabella's capital which is right beside him (eww risky), but with some fancy trade and world congress stuff, he crawls back at me

William (Netherlands)- He is my friend in most of my games if Netherlands is present. We started to fight Suleiman together because he is disturbing my peaceful neighbor Babylon, and then Russia - Catherine, Germany - Bismarck, Persia - Darius, and Polynesia - Kamehameha followed us to fight Suleiman - Ottoman. Man.. the whole world except Maya and Mongolia is denouncing him xD

Enemy (or hated) :

Isabella (Spain)- actually, her voice acting is horrible, and excuse me ma'am, I'm playing as Indonesia and need a rapid-out-of-home-island to make use of my UA. You don't like it ? k. BUT STOP DECLARING WAR AT ME with your cheap navy while my ships are always on guard. Oh, thanks for the denounces from you too, another leader, even my bro Genghis denounced me.. say good bye to Madrid, ma'am.

Suleiman (Ottoman)- He is, unsurprisingly, aggressive.
He declared war at Babylon in the south, which is in the northern part of my border. As my Korea-Babylon armies were not enough, he continue his warmongering at Netherlands in the west, whom just regain its capital from Napoleon - France.

And he declared war too with my friend Polynesia at the east, and Germany took the chance to back-stab Polynesia, while they just declared a friendship about less than 10 turns.

I don't want him to took all Babylonian city and being close to me to invade me, even I got the "pointiest-stick", so I propose an open border deal with Babylon, and then put all of my armies near Suleiman's city even in peace times.

Favourite:
Ramesses II- So long, and thanks for all the wonders!
Enrico Dandolo- This guy is more like a benefit than a problem. He can't steal future city locations you want, he sends you tons of trade routes if you're his friend and he is a great trade partner considering his riches. Also this AI sucks at playing him. And although he is very likely to backstab he never does it directly. I saw him pay an AI 2 continents away to somehow attack me once.
Casimir III- Although in every game he's in he's the runaway civ, Casimir is an extremely loyal ally. Always gets my blood pumping when he's a victory contender. Awesome trade partner too.
Gustavus Adolphus- He's awesome.
Genghis Khan's SAD (Self-Assured Destruction)- What a dumbass. He's pretty much guaranteed to be gone by the Industrial Era at the latest. Why? He declares war on every freaking City state he finds and never takes them over simply to get every AI pissed at him. I think you know the rest. Why do I like him? I'm guaranteed one less d-bag than what I asked for.

Most Hated:
Maria Theresa- She talks WAY too slow and ALL the damn time. More annoying than hated.
Alexander- Going for a diplomatic victory? SCREW YOU. You aren't getting one as long as this warmongering jerk is in your game. Not going for a diplomatic victory? SCREW YOU. If you even get close to winning he will declare war on you regardless of your DOF and trade deals.
Ramkhamhaeng- This guy is way too freaking sensitive. You declare war on ANYONE, even if you get pulled into a war cause of pact after the guy who declared war on the pact BACKSTABBED,he will denounce and DOW you with his 20 city state allies. I wouldn't be surprised if he declared war on you for beating up barbarians attacking his city.
Attila: How does the most aggressive AI in the game get so damn rich? I once saw him with 15k. Also if he declares war on you in the ancient era, God help you. But then again he's the Scourge of God so that won't matter.
Wu Zetian: Go away. You hate me no matter what I do, nag me for the same trade deal 7 times in 10 turns that I already refused and denounce me for no reason. I raise you the finger Wu.
Boudicca: Why won't you ever forgive me for declaring war against someone everyone hated 200 turns ago? I just wanna be friends. *Denounces*. You know what, f you and your religion. I'm here to spread the word of my fist to your face.

Bonus!
My civ 5 friendly rival: Dido
Dido is a backstab happy jerk and always one of my neighbours, but we have good times together. First she backstabs me, then attacks for a few turns before running away, no one hates her for backstabbing, then we make peace and are friends again. A pretty likeable leader once you get to know her. The thing is though, I count how many times she's backstabbed me throughout the game and build that many nukes once I discover them. "You think I just forgot about all those times you backstabbed me!? Think again, BEEOTCH!

Not a lot of favorites, but:

Genghis Khan: As others have said, he acts like a loyal bro. PITA if you've got good city-state relations, though.
Shaka: I'm his bestie in my current Morocco game, and he keeps taking care of troublesome civs for me while I keep my victory in sight and don't have to wage war myself.
Monty: Almost never DoWs me, and since I tend to play financial civs that's all I ask for. Since everyone else hates him, it makes it easier for me to deal for whatever luxes he actually manages to develop two of. This is kind of a theme with a lot of my faves, actually.
Pachacuti: Always peaceful, always fair, never seems to understand how to play up the Incas' massive passive benefits, which is bizarre but good for me.
Attila: So backstabby that he is positively adorable, and unless I start right next to him it's not actually a problem. Since I almost never play on Pangea, and favor watery maps, he's pretty neutered, and will usually just send an army to crash against me every twenty-to-thirty turns, give my standing army a free workout and some promotions, and then sue for peace with a decent payout. He's like an ATM.

Least Favorites:

Alexander: Too good. Too aggressive. Too frustrating. Too smug. Maybe the one case where the AI is reliably better with a civ than human players are.
Isabella: Self-righteous religious bigot. I'm not sure how much she has even mechanically messed with me in games, but know this: I am never a warmonger unless I'm trying very hard to be and even then I don't have instincts towards it. If I see Isabella I will wipe her off the map and damn the consequences.
William: Maddeningly bad at playing his own UA. I'm guessing that his traits are skewed towards "shrewd trader" and that just means "demands more" in the code, but his UA is exactly the opposite of that, giving him benefits for being willing to give up more, and makes it impossible to trade with him even though he should be the Sears & Roebuck of civs.
Oda: So guarded that it makes him impossible to deal with. God help us if he's occupying an exploratory choke-point, because you'll never get an open borders treaty with him. Basically, he's like Madagascar in Pandemic.
Hiawatha: Just occupies a dead zone, and expands it like crazy. Doesn't develop his resources, so it's no use trading with him, and his forest bonuses make it not worthwhile to try to take him out. Even if I wanted to, he has awful taste on where he places his cities.

Special Mention:
Pocatello: I don't know what it is, but I kind of have to take him out on general principle. Thankfully he's got a lot of juicy territory as reward.

Honorable Mentions:

Dido: Good to trade with, will likely backstab, that will probably not be a big deal.
Kamehameha: Only really a problem if you're trying to found the WC. Otherwise a good dude.
Wu Zetain: I've never had a problem with her backstabbing, but she can be a bit expansive and there's not a lot of upside to standing up to her about it.
Casamir: So nice, so kind, so friendly, so why do I only ever encounter him in games where I'm trying for domination and he's then my biggest hater. Hair-trigger warmonger penalty.

Favorite

Alexander. Not so much him, but his horse. Bucephalus is so much fun to watch because he is so expressive! I especially like the first time we meet, because that horse is just overjoyed to be seeing me. When Alex's moods change, his horse's moods also change.

I always make sure that Alex is in my games.

Least Favorite

Enrico Dandolo. I love his voice, but he kills city-states. And I like city-states.

For the same reason, Maria Theresa is a runner-up. However, the danger of annexation from her is easier to spot.

I try to hamstring both of those civs, whenever possible.

Favorites:

Alexander: He's a reliable pain in the ass, but you know what? At least he's trying. He makes the game more competitive without needing to load up every other AI with crazy bonuses (read: Deity difficulty). He contests City-States, goes to war when it'll benefit him (but without the suicidal impulse of the pure warmongers), researches techs, and takes an interest in his culture. In the future, more AI should be modeled after his.

Suleiman: Kind of an Alexander lite. Again; not afraid to contest you for a city-state, makes war of opportunity, and plays the religion game pretty well without being a prophet-spamming douche. Settles good locations but I've never seen him settle crap.

Least Favorite:

Elizabeth: This whiny little complainer will never, ever befriend you for any length of time. Problem is, she's so goddamn incompetent that her best attack against you is a creative form of suicide. Current game she's super-obnoxiously forward settled me, more or less forcing a DOW. I take her capital with Bismark's assistance, and call it a day. About 15 turns later she forward settles into the turf I've taken from her and splits my City Connections. What's a man to do but burn that city down? Suddenly, I've got to deal with a 4-way DOW once I'm done with her.

Haile Selassie:
Dude. Don't great prophet my city. You know this will end badly for you.
Don't do it, man. I'm telling you not to.
You know what? I'll forgive you one city. Just don't do it agai-
DID YOU JUST ROLL TWO MORE PROPHETS IN? That's it... BLOOD FOR THE BLOOD GOD.
[time passes]
Wait, did you even have any follower beliefs that you'd profit from converting me?
No?
You're such a moron, Haile.