There were a few things that made PC-98 games look so unique.

First, it's the combo of resolution and small palette. Western games of the era could default to 320x200 in 32-256 colours (Amiga and VGA) and deliver a colorful image that doesn't really have any prominent details. Check out this Amiga's version of Monkey Island 2 in 320x200x5bpp. Japanese games needed horizontal and, preferably, vertical resolution, so 640x400 is a must. In 16 colours, that's 128K; twice as much as VGA's 320x200 in 256. If you had more RAM, you'd better have more video RAM pages than more colours, too.

Second, the palette isn't fixed. In the PC world, there were "Super EGA" cards that allowed custom palettes, but if you can have 256 colours, even if the resolution is lower, why bother?

Third, PC-98 were "all business", and the video chip there had no sprite support. Redraws were slow, static images and games with menus made more sense than animating moving elements.

As PC-98 was "serious business", such games were also targeting adult audience and had nudity. Seriously, you could buy a strategy and accidentally it might have some nudity and sex scenes in it. But whether you like nudity in games or not, you probably can agree that the work of the PC-98 game artists is remarkable.

Here are a few close-ups of 16-colour images from "EVE" and "Yu-No", some of the most famous PC-98 era games. You can see that artists trade off some of the resolution for dithered colours, but thanks to the gigantic screen size, lots and lots of the details can be added.

Like, seriously, the coat hanger on the first screenshot isn't even taking a quarter of the resolution. How. What.

And I was looking at all this on LCD, mind you. I have a CRT, and I have no doubts things look even better on a CRT, but it is busy at the moment, so maybe some next time.