Resident Evil 2 actually has some of the best voice acting in the series. This is, of course, not saying much, since Resident Evil has long been famous for horrid, hilarious acting. But I think it's worth pointing out that there are many subtle layers of badness when it comes to acting, and RE2 at times is so significantly better than RE1 (and, if you ask me, many RE games that followed) it comes as a shock.
The writing is still hammy, but the voice actors do a better job of making it feel believable. I am thinking mostly of Sherry here, the lost little girl you are supposed to protect in Claire's scenario. She sounds more like a real little girl than almost any other character I can think of in a localized Japanese video game. I dunno who they got to voice her, but whomever she is she's really good. Sherry sounds entirely like a natural, native English-speaking 11-year-old. This may not seem like an achievement, but when you compare her to the often grating attempts by English-speaking voice actors to approximate Japanese archetypes she's a refreshing contrast. Steve Burnside in Resident Evil: Code Veronica, for example, doesn't sound remotely like a real English-speaking teenager. He sounds like he's being goaded by a Japanese voice director to match the inflections of a Japanese archetypal teenager. There's not a shred of this sort of arch phoniness in Sherry, which makes her a surprisingly compelling character.
I played RE2 so long ago (back in 1998) I'd forgotten all the subtle touches that make Sherry and Claire's relationship endearing. Sherry has some very simple A.I. that, from the perspective of 2009, at times reminds one of Yorda in Ico. She runs a little slower than Claire, so that if you run for too long Sherry will be left behind. This often happens without you realizing it, not becoming clear until you try to exit a room causing Claire to say "I can't leave Sherry behind". When you go find her, she's always sitting by herself in a corner, arms hugging her legs, staring at the ground. When you get near her, Claire's head will automatically turn to look at Sherry, and Sherry's head will automatically turn to look at Claire. After a few moments of this connection, Sherry gets up and follows again. All the time Sherry is looking up at Claire as she walks, even when Claire is fighting zombies. When nothing is happening, and both characters are standing still, they will just look at each other. If you stand still long enough Sherry will actually run to Claire and hold her hand. I like the economy of this animation, since Claire doesn't change position at all--it is simply Sherry reaching up and touching Claire's hand. She then just stands there, staring up at Claire, until you move again. Sherry will even hold Claire's hand if there's a gun in it, which seems incredibly cute to me, like she's so desperate for contact she'll wiggle her hand in between the gun handle and Claire's palm if she has to.
This is all ridiculously simple. Sherry's behavior is not some massive feature; just a small detail. But it's a wonderful detail that does quite a lot to suggest a relationship between two characters. This, combined with surprisingly good voice acting, makes the experience of playing Claire in RE2 one of the better examples of an emotionally compelling sidekick I can think of, at least in the game's I've played. One imagines this is what a good game based on the Ripley/Newt relationship in Aliens would be like. I especially like how the behavior suggests particular psychology. Sherry is a neglected, introverted child. You get the feeling (through various story cut-scenes) that her parents don't care about her much. The way she simply "gives up" when Claire gets too far ahead indicates this. She's used to being left behind, and she deals with it simply by shutting down. This makes one feel pretty awful for leaving her behind, even though it has no adverse effect on gameplay. It makes going back to find her not just a simple gameplay hurdle but an act of proving to her that you're not like her parents.
All this makes me wonder why there aren't more children as sidekicks in video games. Most of the other characters I can think of that function in this way--as sidekicks you have to protect--are grown women being protected by men. Although many of these games are good, they always have to explain away the annoying gender politics through some complex reasoning, like Yorda in Ico being mute or Emma in Metal Gear Solid 2 being drugged. But when you have an adult protecting a small child the relationship feels more natural. Of course you'd have to watch a kid at all times; of course they'd become paralyzed with fear when cornered; of course they'd lag behind; of course they'd become emotionally attached to you. They're a kid.
A lot of the believability problems of a video game protector/protectee relationship are solved (or, at least, given a more compelling explanatory framework) by simply making the relationship one between an adult and a child. That is, after all, the inescapable subtext of any such protector/protectee relationship: that you are an adult and they are a child. Ico, for example, forces you to treat Yorda like a child, which makes it necessary to explain why she would act like one. The explanations can range from the rational ("She's been abused by her mother.") to the offensive ("She's a woman.") The nice thing about RE2 is that it simply avoids this by making the player character a confident, focused adult woman and the sidekick a little girl who, quite believably, is scared shitless by zombies and needs help.