I'd sort of stayed out of this discussion until now because honestly every Civ that's been eliminated at this point (except maybe Matthias and Simon, who went too early) is either so fractionally worse or fractionally better than a hypothetical 'generic' Civ with no bonuses at all that I just didn't care. You may as well lump everyone kicked out before this point into the same B tier. Unlike Domination, where every Civ has different UUs at least, or different rates of Science and Culture and Gold all of which feed into Domination, Religion is much less strongly linked into the other mechanics in the game. Early on you need good Culture to hit Theology and good Production to get a Prophet fast, after that it's really just Faith and combat bonuses to Religious Combat. Most Civs can take or leave Religious Victory either way.
However, now we're down to a core of Civs that almost all have more substantial relation to Religious Victory, so I'm popping back up. Surprised Wilfred lasted as long as he did, Tundra bias alone won't make a good Religious Civ when you have terrible production and are slow to get up Holy Sites, and his unique units don't lend themselves to correctly timed Golden Ages as easily.
Amanitore/Nubia [11]
Chandragupta/India [16]
Cleopatra/Egypt [7] (6+1) Not that I think Cleopatra's the best on this list, but she's certainly not the worst. Bonuses to district completion should never be overlooked because of the difficulty in securing a Prophet at higher difficulty levels. Additionally, her unique units are in the right eras to get Exodus of the Evangelists very easily for early spread.
Gandhi/India [22]
Genghis Khan/Mongolia [22]
Gitarja/Indonesia [20]
Gorgo/Greece [19]
Harald Hardrada/Norway [4] I did think about downvoting Harald. Stave Church comes too late to be useful, Harald doesn't have any particular bonuses to early Production, and to get the large Faith and Culture boosts, you need to put Production towards units which slows down Holy Sites. Harald's real secret advantage is early access to transport overseas, but this really isn't enough to carry him any more. However...
Hojo Tokimune/Japan [26]
Jadwiga/Poland [21]
Jayavarman/Khmer [17]
John Curtin/Australia [5] (8-3) ...it is enough to keep Harald over Curtin. I can't work out why Curtin is here, aside from being good generally. The following things make a good Religious Civ: 1. Being able to get up Holy Sites fast so as to secure a Prophet (or having some other way of securing a Prophet); 2. Being able to generate lots of Faith; 3. Having enough Culture to rush the key Civics; 4. Having bonuses to theological combat or spread or religious movement. I don't think Curtin excels on any of these. Curtin has no bonuses to building Holy Sites, unless someone declares war on you extremely early in which case you have other priorities. He has no specific culture bonuses except a very slight one to correctly placed Theatre Squares, and you need to have your Religion up and running well before you've had the time to throw down a load of Theatre Squares. He does not have any bonuses to theological combat or spread or religous movement. In particular, he does not have the UU/UBs in the right era to reliably attain Exodus of the Evangelists when you need it, and reliability in hitting EotE is crucial in getting a Religious Victory rolling at good pace on Deity.
In and of himself, he has no real bonuses to Faith aside from a very slight one for careful Holy Site placement. The sole reason Curtin is good at RV is if you can snatch Earth Goddesses, which combined with his ability means he then gets some really nice bonuses to Faith output. The trouble is... you can't hang an entire Civ on the chance you manage to snag the right Pantheon, particularly when Curtin has no particular means to guarantee getting that Pantheon or achieve it faster, and when in both Deity and MP it's a really popular Pantheon that goes very quickly. It's time for Curtin to go, he is to my mind clear the worst here, at least Harald can get EotE better and can spread more widely and has both of those two things without access to a bit of early-game luck.
Kupe/Maori [19]
Mansa Musa/Mali [24]
Montezuma/Aztecs [14]
Pachacuti/Inca [10] I see you Pachacuti. Pachacuti has basically absolutely nothing for RV except correctly timed UUs/UBs and a bias to Mountains, except the bias to Mountains will still sometimes only give you 2 or 3 and not well placed. I do think he's a bit more reliable than Curtin, but it's not hugely, and Pachacuti being 6 points ahead of Harald and 5 points ahead of Pericles (who is actually fairly decent at RV and gets more relevant bonuses than just a start bias) is bizarre.
Pedro/Brazil [21]
Pericles/Greece [5] I struggled with Pericles because there's two things going on here. Pericles is actually quite good at Religious Victory. Not top tier, but the extra policy wildcard means you can guarantee a useful Pantheon for generating Faith good games, and you can control the relevant Religious City-States very easily (albeit this makes you a bit dependent on Yerevan etc. being in the game), and he has good early culture, and his UUs are correctly placed for EotE. You really can't underestimate Religious City-States for Faith Generation, though - +2 to every Shrine for a level 3 with a single Religious City-State is a lot for a very small investment, and it's reliable and requires no fiddling with adjacencies. Pericles played correctly definitely generates as much Faith from using his extra envoys as any of the bonus adjacency civs.
The problem is not that Pericles is bad at Religious Victory, but that he's much better at Culture victory, and you can't focus on both of these at once, there's too much to build, so you're not making best use of Pericles. It really depends how we're seeing this game. I am imagining it as: "Who would you rather play in a game of Civ VI where only Religious Victory is turned on?", and so Pericles is a good choice there. Others seem to be interpreting it as "Which Civ is most likely to win a Religious Victory in a normal game of Civ VI?", in which case Pericles is quite low because he'll normally be doing Cultural Victories for which he is the pre-eminent Civ.
Either way, however, there's no way there should be a 14-point gap between Gorgo and Pericles here, they're not dissimilar enough in respect of Religious Victories. I think I will upvote him next time, he's definitely better at Religious Victories than Curtin or Pachacuti.
Peter/Russia [29]
Saladin/Arabia [28]
Tamar/Georgia [22]
In general, I'm pretty skeptical about all the Civs that are now really just relying on a) good adjacencies and b) managing to pick up a very specific Pantheon. It couldn't carry Wilfred, it's not going to carry Curtin or Pachacuti either. I'm actually surprised Matthias went before these guys, when he can control Religious City-States better which is a great source of Faith and other bonuses, and has Pearl of the Danube for faster Holy Sites.
I'm also really confused the poster above me upvoted Gorgo but downvoted Pericles... they're almost identical for the purposes of RV except Gorgo's culture is marginally more front-loaded which is a bit better but not much...
EDIT:
@TCBB - responding here so as not to make a new post. My trouble with Pachacuti is that a) his start bias isn't perfect, and as mentioned about 25-30% of the time I get maybe two-three mountains rather than a range, and if that happens he has literally *nothing* for an RV, and b) even if you do get a lot of mountains, he still needs Earth Goddess as your Pantheon and if you miss it that's that. It just isn't reliable. I wouldn't put him above Pericles or Gorgo for the following reasons:
1. Pericles and Gorgo get better culture to hit Theology faster.
2. Pericles and Gorgo can control Religious City-States much easier and I think people are completely under-playing how valuable Religious City-States are. That's +2 Faith in every Shrine across your whole Empire without even having to work any tiles. Okay, you might not find one... but that's Pachacuti's problem too with Mountains, and comparatively, it is more likely that Pericles and Gorgo will be able to control a Religious City-State with all the extra envoys than Pachacuti will be able to lock down Earth Goddess, a hugely desirable Pantheon.
3. The best way for Pachacuti to get Earth Goddess is to go with the +1 Faith/+1 Gold policy... but then you have slower Production than everyone else and are more likely to miss a Prophet.
I think when you roll Pachacuti
just right, and the luck goes your way in the opening 25 turns, his peak potential for Religious Victory is a lot higher than Pericles or Gorgo. I'll grant you that. But Pericles and Gorgo both have a good consistency here that should not be underrated. They're much less dependent on getting the right starting layout and the right Pantheon.