Final Fantasy 4 (Advance):
Cecil: 8.5/10. He gets progressively worse as the game goes on to some degree...but it's more a technical thing because Dark Knight is overpowered, and he's at his worst still a strong, reliable tank with some battery healing.
Kain: 4/10. Cecil without Cover, or his unique swords...or battery healing. He's not worthless, but he definitely doesn't feel very good either.
Rydia: 8.5/10. Blows up second half of the game well, we've covered her well.
Tellah: 6/10. He completely wrecks his first dungeon, kind of lackluster outside of extra MP for healing on Ordeals, then becomes your only healer for a stretch of the game. Limited MP hurts, but he can use Osmose on Cecil if need be.
Edward-C: 2/10. I think people are a tad harsh on him; he still status' enemies when he's in the game. THat said, he still has bad stats, crappy damage (he can use Bows to mitigate this I guess but his damage is never enough to care, so the status you get is better), and Auto Hide is the dumbest ability ever.
Rosa: 7/10. Rosa has this problem that, like in FF5, healing is lackluster in-battle until Curaga. She has a few status moves and works as a battery healer, but she's not as useful as you'd think your primary healer would be until she gets Curaga. That said, she still is kind of necessary at times, but not as effective at her role as Cecil and Rydia are at theirs.
Yang-C: 5/10. He can hit a few weaknesses here and there, and has status claws but yeah.
Palom-C: 6/10. Wrecks Ordeals, does good in Baron Underground, sucks against the bosses...yeah, I'll give him above average for the time he's in your party.
Porom-C: 3/10. See that rant about Rosa? Yeah, Porom has that issue but never exists long enough to actually make up for, combined with being made of paper. Palom can at least kill things fast, Porom is a case of "your healer is one of your first to die."
Cid-C: 4/10. He's a warm body that can take hits well, and Gaia Hammer is nice for the small stretch of the game he has it.
Edge: 5/10. He can pull clean up work after Rydia if need be, and a number of gimmick physical set ups. He's just very hit or miss at times, enough that I think average works.
FuSoYa: 6/10. Tellah in a late-game dungeon...with appropriate scaling...so yeah, same score. To be fair, Rydia and Rosa steal some of his fire, but he's likely to know things they won't, so he's still arguably better.
Edward-A: 4/10. Ok, he's good on specific enemies, kind of crappy on other enemies, and worthless on Zeromus. He is really good as an item boy because of the speed though!
Yang-A: 7/10. What happens when Yang gets a nice fat upgrade to a number of stats, especially speed, and gets a bonus factor of owning Behemoths for Free with Build Up. Also his species claws are useful!
Palom-A: 6/10. In the end, he's still a lesser Rydia, but having a 2nd cannon isn't necessarily a bad thing, outside of Zeromus.
Porom-A: 6/10. Comparable to Rosa; she's got better speed and insured to resist all 3 elements, freeing up a Protect Ring, but the significantly lower HP hurts.
Cid-A: 4/10. He's comparable to Kain. Slower, but way more HP and an actual attack stat, and takes hits better. Also he can murder machines well. Given I gave Kain a 4/10, I feel Cid should at least get the same score, though you could argue FF4a Kain loses a point specifically because he has competition for that 5th slot now.
Final Fantasy 4: The After Years:
Ceodore: 8/10. Good equipment, and stats that aren't HP (which is mostly "low for a tank") on top of being a 2ndary White Magic user, most notably gets Blink and Haste which are extremely valuable, as well as a few other handy spells.
Biggs: DNR. Yeah, probably shouldn't have put them here.
Wedge: DNR. See above.
Cecil-T: 3/10. He's awful when he first joins, and by the time he's not awful, you've already gone through 80% of the game, and he'll be underleveled. Let's assume he does catch up however...why would you use him? He's slower than Ceodore and Kain, in a game where Speed is harder to boost than Strength no less, and Cover < Blink (let alone Haste) which both PCs learn. Add insult to injury, he's got a worse weapon set, not being able to use Lances, thus restricting your character usage (again, something Kain and Ceodore don't do.)
Rosa-T: 7.5/10. Pretty much her FF4 Self, only in a game that calls on her skillset notably more.
Cid-T: 2/10. Ok, he just sucks in this game.
Kain-T: 8/10. Stupid game and your Kain fanboyism! Anyway, variation of Ceodore, has higher HP, but misses a few White Magic spells (like Cuaraga), though still gets important ones. Jump is also there, but not convinced its useful, and Ceodore I think gets more Bands anyway, for all that many don't use them.
Rydia-T: 7.5/10. Her FF4 self but lacks summons for a large part of the game holding her back some. She can item cast healing rods at least and be a makeshift unlimited healer for earlier sections, which hurts the use of another character more so than help her own.
Luca: 4/10. Also bad, but unlike Cid, she's at least invaluable as a tank during Rydia's scenario, and Big Throw does let her get around Moon Phases.
Calca: 1.5/10. Well, he can do stupid good things SOMETIMES, other times he just sucks it up. On top of that, bad stats across the board unless you get some stupid good gear.
Brina: 2/10. Sometimes she'll heal your team, most of the time, she's Calca but defensive. Given Rydia's section has a Black Mage but not a white mage, I'll give her the extra half a point!
Yang-T: 7/10. Solid physical fighter.
Ursula: 7/10. Variation of her father, hard to say whose better. She's faster, he's more durable and hits harder, but she has female specifics which while not better than universal gear, do allow for more flexible equips (dropping down to Minerva is a less hit to Ursula than whatever Yang would drop down too.)
Palom-T: 7/10. Lesser Rydia, but still solid at his role.
Leonora: 2/10. Ok, she has healing, that's cool and all, and basic black magic! Oh look, there's 2 OTHER WHITE MAGES who are better than her at that role, and the offensive thing loses all purpose since Holy exists on both of them, which they learn before she gets any worthwhile Black Magic. She's not even that good in Palom's story seeing as Palom's generally just nuking everything.
Porom-T: 7/10. White Mage Porom, so pretty much same applies.
Edward-T: 5/10. Makes a good healer with some set ups, but he lacks all the perks White Mages have, so he has a lot of competition for slots.
Harley: 0.5/10. Has no redeeming qualities whatsoever. I'd give her a 0/10, but at least she can throw items, and sort of does stuff during Edward's section, but good god what were they thinking with this character? It's like the FF3 Scholar without forcing the Hyne fight to make them pretend they're useful.
Edge-T: 7.5/10. Red Mage-like character, oddly enough, and pretty darn good at that.
Gekkou: 5/10. He's got durability, and I think Shuriken is good for bosses. It's not a lot, but I can see making some use of him.
Izayoi: 3/10. Meanwhile, she's just worse than Edge in everyway that matters, and by a significant amount.
Tsukinowa: 4/10. The one thing he has going for him is that MT Physical Band with Edge that was good for groups in Edge's story, that's about all he's good for.
Zangetsu: 3/10. Oh look, Ninja FF4 Kain!!! ...yeah no.
Golbez: 8.5/10. Overall MVP I'd say. He carries your team entirely through most of the final parts, and in the final dungeon, he's STILL got good damage because Black Magic, has a good physical so he can conserve MP if need be, and shows no real signs of lacking durability. He even has an amazing equipment draw, allowing both flexibility in your team, and letting him adapt to certain boss fights (Hi Omega, I hope you like a Thor's Hammer TO THE FACE!)
FuSoYa-T: 6/10. Worked for his role during Golbez's chapter, which is all you really need from him.