First let me preface by saying, that I don't know what Katawa Shoujo is doing here. I have no problem with that fact, but it seems to me like a "1 of these things is not like the others" kind of deal. At any rate, I looked for completed works by weighted rating, and here we are, even though I read Katawa Shoujo a long time ago.
Just a couple more things: I can't do a short review on a "pure" (and somewhat long) visual novel. I'll try my best to be synthetic, but there's a lot to talk about. Second, Katawa Shoujo is NOT a top tier visual novel. I think it's fine that it's highly rated, and I would add that it's an excellent starting point for people who want to "get into" visual novels, but keeping expectations a bit on the subdued side, might be in order.
Moving on to the "meat and potatoes":
- Setting - The entire twist of Katawa Shoujo lies here. You are still in high school with cute girls, but all of them have some sort of disability. The title didn't need anything else to stand out, and they make sure to remind you of things like an "armless girl", having trouble to dress on her own. Your brain will remember Katawa Shoujo, on difference alone.
- Pacing - Everything moves very fast (short heroine routes) and it's well structured. The choices aren't always easy to understand, but common sense gets the job done, and experiencing the not so good ends is intended.
- Lily and her route - The weakest route, but the best heroine, from a romantic POV. Whoever wrote Lilly's route, must be familiar with 90's live TV, and filling up something with nothing, while waiting for an occurrence. The conflict of interest is made apparent in chapter 2, and only gets disclosed by chapter 4. In the meantime nothing happens. Lilly herself is a delight though, "wifey material" by any standards. Lily's disability is the least addressed out of the 5, and it stays on simple "seeing" remarks.
- Hanako and her route - The "white knight syndrome" triggering route, meaning it's impossible to not like, and want to help Hanako. At first it seems like there is nothing there, just a lot of trauma and pain, but this is not true at all, and the final stretch of the route really paints Hanako in a great light. Hanako is a "girl's girl" if you will, and shows some jealousy and assertiveness, when you were expecting a rescued puppy and submission.
- Emi and her route - The more traditional route, with the most teenage like girl. I'd put this 1 above Lilly's, but the theme (fear of losing something precious/ guarded behavior) has been explored to exhaustion in other works. Emi fits an energetic (Genki) archetype, and she just needs red hair and calling you senpai, to be an obvious staple of most romance visual novels. Nothing bad here, just a lot of "non-originality". Emi's disability is well thought out though, with a flair for the dramatic, but good.
- Rin and her route - The reason why you should read Katawa Shoujo, and your only bet at finding greatness in Katawa Shoujo (Read Rin's route first, do as you like afterwards). Rin's route addresses many interesting notions: The difficulty of understanding your own feelings; Why in the end you will always be alone (you can't be "inside" someone else); Trying to find purpose when there's nothing to drive you; Who you are changes even if you try to "stand still" it etc... It's a bunch of philosophical stuff that has no clear answer, but everyone thinks about it at some point.
The beauty of it all, is in the 2 characters and how they are portrayed. Romantically, it's a bit of a stretch, but from a simple perspective of 2 human beings trying to understand each other it's close to brilliant. Rin herself, is also one of the more unique characters you will ever see in a visual novel. I don't know any "artsy people within the spectrum" in RL , but Rin is a likely depiction of such.
- Shizune (and Misha) and her route - This one tries to do too much, without enough "runtime" to back it up. The comedy and slice of life, are much greater than in the other routes. Shizune, Misha (their personalities) and the "triangle" with the protagonist, needed a lot more events to really sink in. On the other hand the essence of the title's setting is properly portrayed, and Shizune's disability is well handled. The girls begin the route working like opposites that attract each other, but they evolve (show more) as things roll by. Misha is immediately likable, Shizune has a lot of good traits, becoming apparent, it works.
- Humor - Not a lot of it and very light. Some chuckles were given, but I'm an easy target. Kenji (the friend), can be funny or exhausting. Shizune's Father is genuinely amusing.
- Visuals - Lots of attention to detail. What you read and what you see match. The dialogues split when more than 1 person talks at the same time, The flashbacks have a dream like palette. The NVL is used correctly on long exposition/introspection etc.. The art itself can't compete with modern titles (even in 2015 there was much better) but it's serviceable (I like Lily's cg's).
- Audio - The biggest problem of Katawa Shoujo is the lack of voice acting. Visual novels need voice acting to really separate them from other mediums. It's very difficult to grasp the true intentions of the writer regarding characters like Misha(who speak for 2), without V.A. Something simple like a "hello", can be delivered in dozens of different ways (ask Samir). As for the music it's very adequate (even moving) but a couple of tracks are loud and out of place. Overall the audio brings the score down, by simple comparison to other titles.
- Writing - Really, really good, but far too prim and proper for the setting. It feels like some characters are training to have tea with the queen in the Victorian era (I'm kidding). I even learned a new word "corrugated". With that aside, Katawa Shoujo is very competent and highly descriptive: The hand is dainty, the arm is lanky, the finger wags, the movement goes gingerly. Lots of adjectives to convey nuances, lots of care and endless revisions of the text (that's a guess), and a bit too heavy on the modal adverbs. There's no spark of genius here, but hard work needs just as much praise.
- H-Scenes - They are just there. You don't read Katawa Shoujo for them. Let me be clear, they went the "realistic" way. All those VN tropes you can think of don't apply here. No build up, no proper placement, duration, quantity etc... They delivered something different, and did their own thing. It's not a turn-on in any way. Sometimes it barely makes sense.
- Score - I'd say this is an 8/10, and I recommend it if you want to try it as your first visual novel. Do note that this 8/10, is not the same 8/10 I would give to one of the "graphic novels" (differentiate) you might find here. VERY different standards, I'm far more demanding when looking at Katawa Shoujo (I know visual novels, I'm still learning about the others).
P.S: There's a lot more to be said (visual novels need more detailed reviews in my opinion), and the vast majority is very positive. I only become this "analytical" with stuff I like. Go give it a read.