Since
Jewelrunna started from the bottom, I guess I'll start from the top.
Top/God tier
In reality, the game is broken by like 15 or so civs. I'm not really sure if you can appreciate this sort of balance, but I think there's something to respect when the grand majority of civs have strategies that are very potent abilities that can make for a great game. Honestly, no civ is really THAT bad. Even civs considered trash tier still have small windows here and there.
These civs though are rather overtuned, and honestly think need multiple degree of nerfs to bring them back in line.
1. Sumeria
Carting into space
As I've said many times, i have no idea why anyone thought it was a good idea to have no tech requirement for these things, since they're just plain stronger than the regular chariot and have zero counterplay. Did they just fall in love with his beard? Well, who knows? By turn 20, you'll have trampled something whether it be barbarians or your neighbor's poor builders. Yea, it's strong and can run away. And upgrades to knights. Meanwhile, Cleoptara cries.
But the thing here is not just the war cart. That's the thing about overpowered civs in this game. It's not just the warmongering. If it were just that, you could leave Gilgamesh in a deserted corner and he'd be sad. That's just far from the truth. The ziggurat is an excellent improvement and can be spammed, giving a whopping 2 science early game. Now you know why AI Phillip seems to refuse to play the game.
But hey, it also gives 1 culture on a river, and a little more @ Cultural Heritage, so Sumeria can go for the flight culture victory. Who cares about your 5 adjacency campus when Sumeria just spits these things out everywhere?
Oh, and Sumeria can treat barb camps like huts. So even with nobody around, there's still that and it's not like killing barbs is hard with war carts. Feel free to farm them for boosts.
I also heard they can levy CS's for cheap, but not that you'd have a use for their weak units.
Simply put, it's pretty much cheating. Yes, other civs can do better than Sumeria on occasion. But when it turns a beginner into a Deity smashing superstar, Gilgamesh truly is the first civ, and probably the last.
2. Aztec
Want to be anything you want to be? Be Aztec first.
If we wanted to see bias in a game, it's pretty evident as Aztec, since you always get era score on t1 for the eagle warrior. Basically, the game saw that you were smart for picking Aztec.
While Montezuma has always been top tier in being politically incorrect, fact is everyone around him is potentially a unwitting source for his great projects. Eagle Warriors already have incredible strength (2 of them can down an early city) but even if you should fail to take anything, you can always kidnap builders and farm city states for them. Basically, you can win even when you lose, and that just summarizes the Aztecs. You don't beat them. You just survive.
And of course the builder ability allows the Aztecs to bypass scaling district costs, which is yet another example of the civ being able to blatantly ignore the game rules. If you hate district scaling, just play them. Now that you can buy spaceports, this ability is not as overbearing, but it's still effective.
This allows the Aztecs to pursue literally any strategy. You want an encanmpment for defense? Sure there you are. Holy Sites? Whatever. Campus? You're boring, but that's fine too.
The combat bonus per luxury is also pretty ridiculous and just scales more over time. Endgame, nothing can beat Aztec troops on the field, though Mongolian and Zulu troops can give them a run for their money. But in terms of versatility, nothing, not even Sumeria, can beat them at that.
3. Greece
The strong only get stronger
Greece has always been a solid choice, but once upon a time, the Acropolis was crap, and Firaxis gave it their blessing (or took it away from the Royal Navy Dockyard, depends on who's telling the story). As much as people comment on how broken the Seowon is, the Acropolis does definitely come close. Yes, science > culture, but early game in Rise and Fall, the bottleneck is culture (especially for Feudalism/Rec History). The thing about it is just the crazy envoy spam that you can save up and simply steal all the CS's... now that liberating CS's has also been buffed in RnF, this just means Greece just takes it all the way to the bank. Build Kilwa Kisiwani and enjoy a potential 15% bonus to a yield if you match 2 of the same color.
But Rise and Fall served additional blessings to the Greeks with the introduction of Dark Ages. Normally, a classical Dark Age kinda sucks, but Greece's extra wild card lets them take advantage of those policies easily. Or they can do what they've always been doing and try to go for Great Generals. The extra Wildcard also allows them much freedom in choosing governments. They can choose Classical Republic without having to hurt for a lack of a military card, and they can have Oligarchy without having a terrible economy. And they'll probably reach Oligarchy sooner anyways. Want Twilight Valor AND Oligarchic Legacy? Why not?
The Phalanx is not that great but when paired properly still provides for adequate defenses-- very nice when dealing with the other sharks in the ocean for sure.
In the past I would have told you Gorgo and Pericles should be counted separately, with Gorgo having the edge, but now it's pretty much like insignificant. Gorgo is better early game, and Pericles is better later on.Still slightly on Gorgo though.
4. Australia
Wanna fight? Cool.
Without a doubt, the Civ 6 meta favors the aggressive military civs because of the small penalties (if any) on military action. So a builder civ really needs to protect themselves; otherwise even if they keep their cities, pillaging will hurt a lot. Of course, that's probably the deadliest part about Australia-- attempting to stop their snowball may in fact hasten it. Australia wants to be attacked, because doing so gives double production. Unlike other situational bonuses, this is very easy to trigger. But even if you don't want to go this route, liberating a city does just as well, and given how CS's drop like flies in Rise and Fall, it's just been an Australian Paradise.
If double production were their only trick, they'd be plenty strong, but we've just got started. Their districts are better if you put them in appealing places. But what improves appeal in Civ? Mountains? What improves campuses in civ? Mountains. Holy crap. I also think they give some adjancency to another
crappy district, but nobody builds those. While Australia won't do well with those IZs, it probably doesn't matter.
Australia also will make always make great use of land, because of the coastal housing bonus. No rivers? No problem. How many other civs can say that? (Well, Germany, but Germany doesn't need much of anything). As a result if you seek the coast, you'll be fine. Coastal river sites are even better as housing will not be an issue for you at all.
The outback station is still a decent improvement, even if it takes a while. It can be good to fill up poor land.
Oh, and they culture bomb on friggen pastures. Given how tile purchasing costs so much over time, and you getting extra tiles earlier in the game, this alone is potent, even if it isn't as good as Russia's land grab ability.
Their UU is probably the weakest thing as it comes so late, but considering it's still a better infantry, it may still see some use.
Overall, Australia is very well designed, because their mechanics flow together nicely. They're basically OP in the right way if you ask me.
5. Rome
Sorry, I'll have to come down there to talk to you.
Rise and Fall was also very kind to Rome. Rome was always sorta good, but Rise and Fall made them even sorta gooder. The main culprit here is Magnus and the fact Legions can chop. The idea that Legions can chop legions that can chop other legions is ridiculous, and suddenly you have a bunch of Roman Nanobots consuming the world. Which really isn't that different from a game of Rome anyways.
Rome as always is an all rounder civ, with the early monuments providing a degree of consistency, though it is slightly exaggerated since the monuments only come with peaceful settlement (guess it'd be broken if you could get them on capture but that's never stopped Firaxis before). The legion is indeed over the top and the fact Rome's government will always be somewhat sooner means they'll be in force. Of course, the Romans need to build an empire too and have many tools for that including the amazing bath, and the faster roads. And some gold or something.
Simple, straightforward, and strong. That's basically what you need to know.
I'll be covering the 2nd half of the t1 civs next, because we haven't found enough ways to break the game yet.