Japanese works are known for paying extreme attention to detail, anime-related media or otherwise. Western works, on the other hand, often focus on the whole picture, the grand scheme of things, moreso than the little links in between. This distinction is quite noticeable in the realm of visual novels, especially when comparing JVN to EVN.
However, rather than listing out a dull compare and contrast, I will simply state the things which I believe more EVN creators should give more attention. And I will also explain how they can go about doing it. The order I'll go in isn't anything special, and although this list neatly comes out to ten rules (a "decalogue"), I may add more in the future. Lastly, do remember that some things can be done TOO much, which is just as bad as doing them too little. Balance is key.
1. Change the facial expression and/or the pose of the speaking character each line they talk. No exceptions. The game is more immersive this way -- the player is reminded they are in an active, living world.
2. Change the backgrounds often. Watching two characters talk back and forth is boring enough when their faces remain the same! Show us some of the scenery! And also, hiding the speaker's face by a subtle background change can make for an interesting concealing of information for the reader. The visuals tell us just as much about the characters as the text.
3. Keep something animated on the screen, whether it's a blinking sprite, GUI effect, or even so much as the clickwait icon. Again, it reminds us that we're in a living world, not looking at a stiff picture book with music.
4. Add as many sound effects as possible. Once again, immersion is key. Proper usage of ambience such as wind or rain also creates a nice atmosphere. Simply adding it into the game can change the experience the player has. Silence is also quite good at showing tension, but too many EVNs simply don't have music at all, so I wanted to refrain from mentioning it.
5. ...That said, know what sounds are fitting and what aren't. Clips with bad audio quality really break the immersion we've been setting up this whole time. Also, using sparse voice clips in a game without voice acting can be jarring. Like voice-acting itself, if the clips are bad enough, they will be worse than having those sounds left to the reader's imagination.
6. If you are going to include an opening movie, put 200% of your effort into making it. If it looks sloppy, it will certainly come off that way to the reader. Try and hide lots of hidden details into the movie that only a second, third, or hundredth viewing can establish. And these details should make no sense prior to reading, so afterward the reader can go back and say "So that's what that image was!"
7. Add pointless details -- Chekov's guns -- into your writing. Sounds counter-intuitive at first, and if abused your story will become awful. But the gun is more of a double-edged sword. Let me use an example -- say the main character of an otome game taking place in a highschool overhears her crush saying he'll attend the school festival. Now, you can guess what happens next, right? The next plot thread becomes obvious. But if you add in the voices of other characters -- a friend's pet is sick, or the main character's sister is having her own relationship problems, perhaps the reader can't so easily predict the future of the story. I used an obvious example, but more subtle stories can really trick the reader into thinking the plot is headed into one direction when it makes a 180 degree turn. This is a powerful skill that should be used with caution.
8. An addendum to the above: do not forget your plot threads or leave anything hanging. Even if it amounts to nothing, don't tease the reader by mentioning something which never appears again. Introduce them and update us on them, but if they don't need to be a part of the main story, they don't have to.
9. Beta test early and often. Too many games (mine included) are released with bugs everywhere. Demo bugs are usually justifiable, but for a final release, make sure to run through the entire game on multiple operating systems. Go through every route, make sure the game doesn't crash, make sure images, sounds, GUI, and any interactive features are being implemented correctly. And also check for spelling/grammatical mistakes; even if you're naturally good at it, typos can somehow sneak into your story without you realizing it.
10. Create a proper title screen. To go further: create a product outside the story. Add several menu options and functions that can make your game stand out. The more unique art and music you use for these parts, the better. Same for the opening movie - use images (of much higher resolution) that will only appear in the movie and not in the game. Synchronize both the inside and outside of the story, and what you have then is your full game. The VN is not simply an interactive picture-book, despite the popular comparison. There is a reason the VN is considered a video game -- don't forget it.