Godlike:
Yuna (FFX) vs Maya Amano (Pers2) - Not even giving her credit for Aeons, she wins this. Maya's good and beats quite a few people here, but not Yuna.
Rena Lanford (SO2) vs Lenneth Valkyrie (VP1) - Necessary and irreplaceable. Lenneth is awesome, and they finally do that 'Game Over if Main dies' thing in a sensible manner (3 turns before it happens, so you get a chance to reverse it!), but this is Rena's match.
Rika (PS4) vs Alicia (VC) - Haven't played VC, but my kneejerk is other Scouts can fill in for Alicia if necessary... that's not going to beat out Rika.
Heavy:
Claude Kenni (SO2) vs Millenia (G2) - Close. Millenia's availability is limited, but she's normally around for most boss fights, which is the only time in G2 you might need her level of broken. Claude is replaceable, though there's no need to do so.
Kika (S4) vs Maria Traydor (SO3) - Kneejerk.
Yosuke Hanamura (Pers4) vs Nina (BoF1) - I really liked using Yosuke, but he always felt the most replaceable of the P4 group.
Middle:
Alice Elliot (SH1) vs Fayt Leingod (SO3)
Crono (CT) vs Hahn Mahlay (PS4)
Angelo (DQ8) vs Jude Maverick (WA4) - Jude has a lot of situational uses, and his speed is nice. However, the amount of turns he gets kind of highlights how little he can do with those turns until late. I wouldn't mind replacing him with say, another Arnaud. If I could replace Angelo, I probably wouldn't.
Light:
Roger S. Huxley (SO3) vs Natan (SH3)
Fei-On (SaGa) vs Jet Enduro (WA3) - Fei-On actually has some of the best innate growths in the game. And he's talented at learning nearly every Fist skill! Too bad that he's not talented at learning DSC, and that his base stats are kinda bad and he's one of the PCs that takes awhile to be able to recruit. Jet's LVP, but Medium twinking, decent speed, and general customizability means that you can make something useful, though generic, out of him like Item-boy, Finest Arts-user, Gatling specialist... Fei-On is twinkable, but less readily available and obsolete out of the box.
Onix- For this division, please vote for the worst of the two given PC's.
Astrid (FE10) vs Luvdisc (RSE) - Well, I'm convinced.
Goof Off (DQ3) vs Red Turnip (SaGa) - Turnip is bad, but if Goof Off is getting credit for turning into Sage, Turnip at least starts with a lot of monster skills that help it get to a good endgame monster form like Kraken. Also, can learn LifeRain, the one really useful thing that Monsters do (especially if you don't want to spend forever getting Mesarthim).
Luke (SF2) vs Sergei (S1) - Luke was the first hawkman you get, right? That's early enough to not force anyone out of the party, so he's at least a useful warm body. Plus he flies. Sergei is useless out of the box in Suikoden *1*.