WALL OF TEXT INCOMING :D:D
Red - I don't think he is well defined, actually. In the beginning, he was like a less sneaky Gold or more civlized Saph. Or a less angsty Ash. Now he's just the plainest character there is. He doesn't have any special traits to describe him other than being the friendliest perhaps. And strongest. Thumbs down
Green (male) - I like him. He is not as silly as Gary or as unreasonable as the game's protagonist. He has a history and he develops over time into someone who can actually be a likeable friend. I love when he trains with Yellow. Thumbs up.
Blue (female) - Just as with Red, I can't really define her anymore. In the R/B, Yellow and C/S/C arcs, she had personality. She was the escaped Rocket girl who knew how to deceive and use strategy, and she was downright funny in the R/B arc. But after FR/LG she's just a plain, kind girl. What happened to all that personality? I don't see it anymore and I'm sad for that because it was interesting. Thumbs down.
Yellow - An original character that I like. I think they gave her an initial adorable personality. She is the most naive and happy go lucky there is, and for long we thought (or were supposed to think) she was a boy. Then, with all her pacifist views and special battlestyle and Viridian powers, she turns into quite a deep character starting with the battle of Lance or maybe even earlier. In the Crystal arc, she shows this further when she tries to help everyone and in FR/LG she is an adorable teenager :D Overall, I think they did well on this character. Thumbs up.
Gold - He's a rascal who cares for gambling and women. I found him awesome in the G/S/C arc for his relentlessness, but in the HG/SS arc it's kind of annoying really, haha. He has got some solid personality traits to lean back on, but I don't really think they have made him that a deep character out of that. Maybe not everyone has to be deep though. He has his principles and he sticks to them no matter what, which makes him uncomplicated. Thumbs middle?
Silver - He's cool. His story and his actions make him cool throughout G/S/C and onwards into FR/LG. He is super serious and a downright counterpart to Gold, which I think Gold needs. I think they took the concept of the game rival and the hint that he is Giovanni's son and turned it into something fascinating with his and Blue's backstory. Thumbs up.
Crystal - One of my favorite characters. She isn't serious as much as she lacks a sense of humor, lol. She has a history too, but I guess she is a bit of a Mary Sue. She is a researcher assistant, she helps children, she is best buddies with a cool team of pokémon, she overcame injury and evil people and became buddies with Suicune, well not really but. Yeah, she's a Mary Sue. It's okay though! For me. But if I'll be a bit less biased, thumbs... uh, Thumbs middlewards.
Ruby - He is a Gary Stu, if anything. He has a "tragic" past, angsty relations to his father, he is good at one thing (contests) and struggles to keep himself from doing the other thing (battles) even though he is really good at it. He is overpowered :p To top it off, he is a gentleman who knows how to dress and behave, and he is quite adorable as well. He's too much for my taste, even though I do like him. They shouldn't have let him steal Saph's battling spotlight so much. So I'm not really sure but I'll just say thumbs middle :P
Saph - she's amazing. Very unique, with her wild life. Her backstory isn't quite as suspenseful as Ruby's, since she can actually talk to her father lol. I think it's adorable how she loves Ruby and want to be girly for him (somewhat). She isn't overly deep, perhaps, not like Ruby. But her concept is better executed than his is. Thumbs up.
Emerald - sadly, I'm one of those people who just can't get past his terrible design. Not even the backstory is enough to justify that. And also, his personality is annoying at best and I really think they should have just gone with Wally instead - Wally was an interesting character! Emerald gets thumbs down.
Dia - He's alright, but there's a hint of Gary Stu in him actually. They centered his personality around some traits that were very definite. Such as him being somewhat slow, a glutton and very righteous and loyal. That's pretty much what he is. He can doze off and be silly and then suddenly act a very smart and brave hero. It doesn't all add up in my mind, and I'm not sure how I'd have wanted them to portray him if otherwise either. Wow that was a strange sentence :x Thumbs down.
Pearl - Okay, I love pearl. He is my favorite character alongside Crys, possibly even more so. He has a history even though we don't get to see much more of it than a bit of Palmer. He is very alike the game rival but smarter I'd say. I love that he is kind of the one who won Platina's first battles by coaching her xD And also his relationship with his pokémon is deeper than between the other Sinnoh dex holders and theirs. I think he is a well defined and developed character. Thumbs up.
Platina - I don't find her bland, actually. Her not showing facial expressions in the first chapters is hilarious and cute, and her helplessness when it comes to doing things in the real world is adorable. Her history explains it, which is what matters the most for me. Later on, in Platinum arc, she turns into a very serious and strong battler which is a biiiit too much of Ruby for me, but I still think she has more personality than Blue. Thumbs up.
As for Black and White, I can't really say much as I've only read some chapters and haven't got a good feel for the characters yet. But White seems like a mix of Blue and Crystal while Black seems like a mix of Red and Gold. Not too interesting characters imo, but I'll read on and we'll see what I think then ^^
I understand that the characters are based on the game ones, where the rival always is a male (even in Unova, there was Cheren too, they just couldn't have let Bianca be cool and actually good!). And I'm not going to argue about that there should be more female dex holders. The authors have a good mix of female and male characters in the supporting cast, with gym leaders and other original or game based characters, so that's good enough for me! A favorite is Marge or whatever she was really called, the Team Magma woman in Hoenn who talked with Ruby on occasions.
tl;dr Overall, I think they have made the characters pretty deep considering it's a pokémon thing. The anime doesn't go anywhere near this, really. And the games don't let us see as much as the manga does, doesn't give as much exposition.
