Final Fantasy 4 (Advance):
Cecil: 7. Solid PC, probably not gamebest, never a liability in parts of the game that matter.
Kain: 6. Equal to or better than Cecil until the Excalibur comes into play, then never catches up again, but still is better than an empty slot.
Rydia: 7. I feel like she's a little overrated, but only a little. Probably has a solid argument for gamebest in the end, it's either her or Cecil, but she has a notably bad start - her offense is pretty much notably subpar for the most part before she learns Bio, and that's quite a while. (-ra spells are good against weaknesses, pretty bad otherwise, while most summons are somewhat badly overcosted and take too long to charge IMO).
Tellah: 5. Warm body, his MP pool is seriously unfortunate and his deficiencies begin to show badly in his second stint with the party. His score is notably higher for his first stint, where basic elements are still useful damage. Still, he gains points for completely trivializing most of the bosses he faces (and loses some of those points for being worthless against randoms).
Edward-C: 1. Itembot in a game that doesn't need an itembot.
Rosa: 8. Significantly better MP-less damage options than Rydia (in fact, certain equipment setups can get her to being competitive with Kain/pre-Excalibur Cecil), then add on the fact that FF4 white magic is mostly great. You'll notice I rate her higher than Cecil or Rydia but don't put her in the running for gamebest PC; my logic behind this is that she functions more as an enabler for the two of them rather than being gamebest in her own right. If you want to split hairs they could really all be 7.5 but I feel like Rydia is appreciably worse in a vacuum where Rosa is not next to her tossing heals and I'm trying to reflect that in the scores.
Yang-C: 6. Solid PC while he's around, durability is a little weird (lots of HP but his defense is kind of subpar at some points).
Palom-C: 5. Black mage who only exists in the pre-Bio phase, but is somewhat saved by Twin. He's mostly useless in randoms while you have him because he just doesn't have enough MP to sling spells that are worth a damn for a dungeon length.
Porom-C: 3. Significantly worse Rosa in a part of the game where item healing solidly outperforms anything she can ever do.
Cid-C: 2. Kain without speed. Not a good place.
Edge: 5. See Super's comments, basically.
Fusoya: 5, see Tellah, most of same issues apply.
Edward-A: 3. Stupid weapon, durability is still a severe liability.
Yang-A: 7. Might have a legitimate argument for gamebest PC in FF4A, but it's probably a bit of a longshot one. Clearly better than Kain for endgame use.
Palom-A: 6. Slightly worse Rydia.
Porom-A: 6. Still significantly worse Rosa, but she's available now.
Cid-A: 1. Same problems as before, now has more competition. Get the fuck out.
Final Fantasy 4: The After Years:
Ceodore: 8. Better than his dad where it matters (Speed), the places where his dad outperforms him are either irrelevant or easily covered by equipment.
Biggs: DNR
Wedge: DNR
Cecil-T: 5. Crippling availability issues aside, he's exactly the same as his original incarnation in a notably more difficult game where he has to compete with better PCs for both his formerly exclusive gear and his party slot.
Rosa-T: 7. Also basically the same as her original incarnation, but her physical has gotten relatively worse and her competition has improved notably.
Cid-T: 2. Basically the same as before.
Kain-T: 8. Even if you don't twink his HP/MP, legit argument for gamebest, his white magic selection is basically perfect for what he does, his damage is great, and his equipment selection is notably better than the original game. +1 if you do twink his HP/MP, which puts his durability into stupidly high levels.
Rydia-T: 6. Basically the same as before, in a game where her summons' charge times feel like they matter more *and* the really good summons are significantly more missable than they were before. Not a winning situation for her.
Luca: 5. Solid, never a liability, also never a standout. Occupies the same kind of place that Kain does in FF4o.
Calca: 1, novelty PC.
Brina: 1, novelty PC.
Yang-T: 7. Has actually improved since the previous game, but not by enough to raise him a point.
Ursula: 8. See Ceodore argument, this one is exactly the same.
Palom-T: 7. Yes I am ranking him above Rydia. Better intelligence, less FAQ-baity for his good damage, and IIRC he gets some of the money spells faster than Rydia does, plus MT Break feels significantly more useful in this game and he gets that earlier too, plus lategame possibility of Dualcast. Sorry, dualcast Meteor is better than anything Rydia will ever do. -0.5 without Dualcast, that said.
Leonora: 4. She is basically Fire Emblem Est logic applied to an FF game, and learns her spells hideously late even if she is in the running for Dualcast.
Porom-T: 8. Basically the same as before but with IIRC slightly improved durability. Is a potential user of Dualcast, and IMO probably the best one, in spite of what Palom gains from it, because *she* gains the ability to dual up MT Curaja->Holy or somesuch.
Edward-T: 6. Best raw healer in the game, at the expense of non-healing support. If you can get that from elsewhere in your party, great.
Harley: 2. Better than Calca/Brina, still terrible. She really wishes she had the dummied Blue Magic command that was likely intended for her.
Edge-T: 8. Improved so much from the original game it's not even funny, and now solid contender for gamebest.
Gekkou: 6. Better Luca. Easily the best of the bonus ninjas.
Izayoi: 3. She's helpful for Edge's chapter, but is pretty crappy beyond that.
Tsukinowa: 4. Notably worse Edge, helpful in Edge's chapter though.
Zangetsu: 2. Notably worse FF4o Kain (not TAY Kain). Yeaaah.
Golbez: 7. Tank mages are awesome. Misses some of the Black Magic versatility that Rydia/Palom get but he does get the money spells and he can do serviceable damage without MP. Carries an underleveled party if you didn't do challenge dungeons and such.
FuSoYa-T: DNR.