Breath of Fire:
Ryu: 8.5/10. Yeah, Boomerang Death God for 90% of the game, has Dragons for 70% of it!
Nina: 8/10. Her only flaw is iffy on damage, but honestly, BoF1 item casting is so hax, this isn't that much of a flaw.
Sr-1: 4/10. Clearly the inferior of the two, but he's still a warmbody who does actual damage.
Sr-2: 5/10. Sr-1 but better in like everyway!
Sr-3: DNR. Joins for like 3 rooms, and there's a very good chance you won't even get into a single random encounter during this section.
Bo: 4/10. Adequate Physical damage for randoms when he joins and your best Boss Slayer until Ryu gets dragons, manages to stay good for a little while longer, but then becomes incredibly obsolete for the entire 2nd half of the game.
Karn: 7.5/10. Awesome speed and a really strong weapon (IcyDr) are available for him immediately, so his pre-fusion Moments aren't as bad as you'd think. Then he gets fusions, and kicks ass; you never have a reason to not use Shin or Puka (I'd say Doof, but having Doof means you have access to Puka, whose better in everyway.)
Gobi: 1.5/10. He does a good job against PincherX, and if gotten enough levels somehow, he's good against Morteo as well! Two fights, whoo? He'd be good in the Underwater Volcano, but being required for Shin makes you not bother using him.
Ox: 3.5/10. He makes a good 4th PC right after he joins since why not, and has some extra healing worth. Also an option to use over Nina or something against Random Encounters until you get Puka. So basically, its a similar case to Bo, only he's not as good during this section.
Deis: 8.5/10. Yeah, overpowered; cannon with massive speed and good HP due to the absurd level up speed, and even has good defense too cause BoF1 is weird in giving THE TWO FEMALE MAGES better equips than everyone sans Ryu.
Mogu: 0.5/10. There's literally one moment you might use him, and its during that short stint where Nina is absent, and frankly, its possible using downgrading to Shin for fusions and using Ox may be better than Mogu. I'd give him points for the Initiative 100% Run...except Deis has 100% Run too *AND* her speed is so high, it might as well be initiative, AND she has a lot more AP to do it with, so even for a niche use like that, he's worthless. Oh yeah, did you know he's statistically inferior to Gobi outside of speed?
Fire Emblem Staves, Light Magic, and Thieves:
Ellen: 2/10. Healer when you have none! ...for like 5 minutes. Really bad after that point.
Chad: 5/10. He pulls his weight before promotions start mattering, and still has thief utilities after. Yeah, average works.
Clarine: 6/10. Iffy offense, but moblie healer and awesome evade make for a half decent unit.
Saul: 4/10. Ellen except has actual stats in areas like Speed. Think he also joins at a level higher than what she's likely to be at that point to boot. Still has no offense before promotion, and can't take hits to save his life, and after promotion, his offense is still kind of bad if he's not hurling Aureola...which takes time t learn.
Astol: 5/10. Chad whose probably got the level edge, but worse supports and joins later...yeah, screw it, same rating. Its also viable to use both characters cause there are big maps with lots of treasures, where using 2 thieves can come in handy.
Cath: 0.5/10. Three thieves, however, no. The half point is quite literally if you need an emergency thief should Astol *AND* Chad both die. Otherwise, she joins waay underleveled, never amounts to ANYTHING useful, and her thief utility purposes are taken up by *2* far superior PCs. To make matters worse, killing her and thus making recruiting her impossible can make your life EASIER, due to how she functions. That's really fucking sad.
Cecilia: 3/10. Uses Anima Magic, and is mounted, so she's not completely awful. She's still a good example of how FE6 Prepromos suck though.
Yodel: 4/10. Works if you want a healer for the last few maps who requires 0 training, but that's all he can do. Coming with the best staff in the game and having full usage of it is pretty nice too.
Serra: 3/10. Only healer for Lyn mode, and first healer in Eliwood/Hector Mode, but she's a pretty uninspiring long term unit.
Matthew: 6/10. Basically Chad/Astol, only can actually do combat late game due to potential promotion.
Lucius: 6/10. Why I never respected Erk. Lucius does all the same stuff Erk does at the same time, but better, and come the final chapter, he's another person wielding a big awesome Legendary Weapon (Aureola.) His high res makes the whole "Loses to anima mages" a complete joke of a WTA to boot.
Priscilla: 5/10. High move healer, and gets Anima magic upon promotion which is somewhat better than Light magic.
Legault: 5.5/10. Overall better stats than Matthew, but joins later, and I don't think their differences were big enough to matter, so yeah, lower rating. I think Matthew may have had better supports too.
Jaffar: 4/10. Workable filler unit if you need one, but not much else.
Renault: 2/10. He's Yodel, except people like Pent exist who can do the Use Staves Awesomely thing just as effectively in addition to OTHER things like offense, let alone Athos joins very shortly after.
Moulder: 4/10. The usual early game healer who isn't very good, except Bishop Class is pretty rocking in this game, so its worth an extra point.
Colm: 7/10. FE Thieving at its finest; covers his bases well, has a quick good support with another solid unit, and the utilities come in handy. The fact that he doesn't lose those utilities upon promotion doesn't hurt either.
Artur: 5/10. Felt like Lucius-, and has to compete with Lute like instantly, so the Erk issue kicks in. FLIPSIDE, he can still become Bishop which makes him awesome in the final stretch of the game.
Natasha: 6/10. Why Moulder isn't that useful; Natasha has most of the same advantages, and has stats in other significant areas.
L'Arachel: 4/10. She's good, and can be promoted early and still have good stats, but eh, still felt like she wasn't quite worth it.
Rennac: 3.5/10. Good second thief if you need one, not much else.
Rhys(9): 2.5/10. "First Healer in the game" thing, only this time Bishop is NOT around, and his liability is even greater, due to dying anytime a Myrmidon looks at him funny.
Volke(9): 6/10. He's functionally your only thief. On paper, he should be higher, but oh god do knives suck. He's still a good evasion tank however.
Sothe(9): 2/10. Works as a second thief for the desert and...if Volke dies...but really, never anytime else. Joins underleveled, late and can't promote. Its like Cath all over again...except he's a free recruit, won't steal your objects, and there's only one other guy he's competing with, not two.
Laura: 4/10. She's Rhys all over again, compounded issues...but being your ONLY HEALER during Part 1 makes her rather crucial, and she really helps out a lot in Part 3 as well, allowing flexibility with Micaiah. Not particularly useful come part 4 though.
Sothe(10): 7/10. Good unit in Part 1 (which really needs him) and Part 3, starts to trail off in Part 4. Thief uses don't hurt either.
Heather: 4/10. Sothe but with far less combat worth, not only due to being worse (especially in strength) but cause she's in teams that need her a lot less.
Rhys(10): 4/10. Dunno, but he felt better here.
Oliver: 2/10. Worthless unless you really need a Tier 3 Healer in Endgame besides Micaiah
Volke(10): 4/10. He'd be higher, but docking him a point for sharing a weapon with another forced PC who does NOT have a unique weapon, making the use of him require you nerf one of the two in terms of their blessed weapon. Additionally, he just joins way too freaking late to really merit being much higher. He's good for what he is, but there's just too much against him to really get much higher.