Throwing my hat into some civ ranking (certain civs haven't been played in a while, but hopefully I have a solid assessment regardless.)
S: Egypt, Poland, Babylon, Carthage
The burial tomb is really the step up Egypt needed to go from a situationally good civ to what seems like a could be consistently great civ. Poland's Poland, Babylon's Babylon, sky is blue, water's wet. Carthage has some very wonderful gold generation going for it though, and if there's anything I LOVE, it's gaining ridiculous sums of gold.
A+: Korea, Maya, India, Aztec, Byzantium, Brazil
Korea's always been pretty heavy with the science. I'd probably put them higher if it weren't so easy to clear tech gaps thanks to tech trading. Without said feature however (or if they just don't like you so no trading) they might be an S-. Mayans + Tradition + Freedom is downright ridiculous. India's very reliable when it comes to getting a religion to spread like butter, and it's population growth is incontestable, even against China. I've already gushed about the Aztec's in their own thread. I don't get why people are throwing complaints and suggestions for them when there are other civs that need buffs way more, but opinions are opinions. Byzantium's also the most reliable religious civ in my opinion. Not too amazing to make it into S, but reliable with a good UU. Brazil I'll admit I have a bias towards. They're my favorite civ in the game, and Papa Pedro is my spirit animal. Regardless, they're in my opinion the best culture civ around, with a pretty solid UI and an okay I guess new UU (it's better than their old one at least).
A : Mongolia, China, Ethiopia, Spain, Morocco, Zulu, Indonesia, Assyria, Celts, Rome, Danish, England
Mongolia's a strong war civ who's ability makes their job easier. I honestly don't know if that's a good or bad thing though, since simply taking city states means you won't get potential EXP. China's great, but not as impressive as India in my book, though they have their own distinct advantages and disadvantages, and have an easier time going wide if they're religious. I have no real gushings over Ethiopia. They just feel like a lesser science civ, but their GP generation is pretty great. Spain is so damn annoying to try and deal with religiously that I knew they'd be A material, though their UU isn't too amazing in my book. Morocco's a great gold civ that's not as impressive as Carthage, but getting there. The Zulu are ATROCIOUS to fight against late game, and as a war civ, they're probably the best. Their lack of versatility however makes me want to drop them to an A-, but what they do well, they do REALLY well. Indonesia's such a good business civ it's not even funny. I don't even care about their UU (which is okay) I'm all about that monopoly corporation life.
Assyria's very tough when they get the ball rolling on their UB, and their science gain is...pretty okay. I wish you could build 3 Seige Towers instead of 2 though, because I've had days where I've attacked multiple cities at once, wishing I could build more ST's but that's a nitpick at most. The Celts are a great religious civ. Just great, not amazing. Rome is fantastic for upkeep in wars, and it's satisfying to take a city and still have enough infrastructure to be worth unpuppeting in the future. The Danish's Berserker is delightful. Probably my favorite UU. They're highly mobile, their UB is great, and they're just all around fun to play as. England...I HATE HATE HATE having you as a neighbor. She's so annoying and unless I completely wipe her out I can't do anything about her stealing until like, TWO WHOLE ERAS. That's what makes her so viable
(But seriously, if that woman steals my culture one more time, I'm going to destroy her.)
A-: Russia, Inca, Shoshone, Huns, Songhai, Ottomans
Now Russia's recently gotten a buff that I haven't been able to take advantage of, so maaaybe move her up a notch in the tier list, but for what she is, Russia's my favorite expansionist civ, with a great UU, and an "okay but I wish it would let me expand even harder" UB. I love everything about the Incans and think their UI is the best in game...they're just not as specialized as other civs above them. F$%K THE SHOSHONE STOP BEING MY NEIGHBORS...Anyways the Huns are definitely my favorite war civ with an army that never seems to stop growing and a strong prescience the entire game. If their UU could shoot 2 tiles away, they'd be an immediate S-, but they don't, which is fair considering their time period, and the nature of ranged mounts. Songhai's mobility is amazing, and it's river yields are beautiful, but there's not much else to talk about. The Tanzamat's a great but admittedly underwhelming UA, but the UB and UU are pretty great.
B+: Netherlands, Japan, Iroquois, France, Portugal, Arabia, Persia
The Netherlands remain an enigma when it comes to trading, but no matter what you do with them, they're still going to be pretty great. The polder's amazing by the way. So very pretty too. Japan is SUPER STURDY, with a great UU and UB, but their UA's never been anything to write home about, and maybe their UB could use an additional bonus or two. The Iroquois are amazing when your forest are abundant, but not the best when they're sparse, so they feel pretty middle grounded to me. France's UI feels like the strongest UI in the whole dang game! As for their UA and UU, they're okay, but not that impressive standing against certain other civs. Portugal's recently gotten some buffs here and there, so they may need to be moved, but from my experience, I've never been wowed by their gold generation. Arabia's UA is just plain delightful, and camel archer's never go out of style. The Bazaar's a fair money maker. Persia has a great UA that ties in well with their UU, but they've never been too amazing for me. Regardless, if you manage to extend your golden ages, they're a force to be reckoned with.
B: Polynesia, Greece, America, Sweden, Siam
Polynesia is situational greatness depending on your map, with a lovely UI (that demands your attention from potential resources), and an okay UU. Greece makes the easiest victory even easier to obtain (though their have recently been changes to the required # of delegates, so maybe I can see myself gravitating back to them in the future), but their UB is pretty nice. America, baby, I love ya, I came from ya, ya got a good UA and a great UU, but you have GOT to do something about your UB. I think it's a good fit for you, and I think your two victory duel wielding is cute and I was very excited when I saw it, but even I can admit the Smithsonian isn't great enough to feel worth the extended wait. It's just "okay", but nobody goes this long through a game just for something that's "okay" unless there's something else that really sells the civ. It doesn't even encourage you to pick freedom (which is a nit pick, but still worth mentioning). Do something with your specialist or Great Person generation to make me want that Freedom junk you're always talkin' about, then call me in the morning and we'll talk about moving you to the A's.
Sweden's UA and UB are great and don't really need changes in my book, but their UB is so thoroughly underwhelming and comes a bit late for my taste. But there's nothing necessarily wrong with uniques that come late, as long as they feel worth it. Siam's does great with it's diplomacy civ bonuses, but it's UB and UU don't really leave much of an impression.
B-: Austria, Germany
It's never been too hard for me to lose my allies, which is why Austria so thoroughly underwhelms me. Germany's got an amazing UB, an okay UA, and a great, but very late UU. I get that a lot of hate gravitates around late game uniques, but I like em. It helps to keep games interesting. With the increase in required delegates, maybe both of these UA makes them unforeseen gems. I'll need to do a game with them in the future.
C-: Venice
Venice will never escape the bottom barrel outside of the OCC where they shine. Considering the fact that you don't get MoV's in OCC mode, I think that's what one should look for if the suggestion for any buffs where to come. I think providing a ton of growth and culture towards border growth in the City State that it buys would be pretty great. All of this said however, I do think the UB's for Venice are fun, and make the game interesting for it.