I’ve played a few games in JP over the last 2 years, but I usually don’t worry much about comprehension when playing a game. If I can understand the basic meaning enough to progress, then I’m happy. That said, I’m more then happy to offer very rough and subjective impressions of language difficulty! I’m putting numbers on these to try and separate them from each other more clearly, but I don’t think it’s a very strong mapping to the book levels on Natively. From roughly easiest to hardest:
A Short Hike, PC, 2019 -- L23?
Not originally in Japanese, but I thought it would be fun to try in JP. I don’t remember encountering any major issues with the translation, and the game itself is very fun and wholesome. No autoscrolling text iirc.
洞窟物語 (Cave Story), PC, 2004 -- L24?
This was the first game I played in Japanese over 2 years ago now, but had no issues getting through it even at the time. It’s not text dense, and what’s there isn’t too crazy either. iirc there’s some autoscrolling text though.
カエルの為に鐘は鳴る (For Frog the Bell Tolls), GB, 1992 -- L25?
This game never officially released in English, but characters from it show up in Super Smash Bros. Ultimate as spirits, so I looked into it and bought a copy. It’s a really fun game, with solid gameplay and great comedic moments, including some meta-humor I usually associate with modern indie games. No autoscrolling text in this one, and almost no kanji because it’s at Game Boy resolution. It’s worth noting that understanding character dialog is crucial to figuring out what to do in this game, because it doesn’t follow a common plot framework at all.
Ib, PC, 2022 (original was 2014) -- L25?
This is a remake of what’s apparently an iconic old RPGMaker game, and it was very interesting. Horror’s not usually my thing, but I enjoyed this one. No autoscrolling text is a major advantage too!
デンシャ (Densha), PC, 2014 -- L25?
This was another really interesting RPGMaker game. It’s a puzzle game with some minor horror elements and a really interesting story with a cool ending. Lots of fascinating ideas here from a puzzle designer’s perspective, and almost no autoscrolling text.
ゼルダの伝説 時のオカリナ (Zelda: Ocarina of Time), N64, 1998 -- L26?
There’s not much text in this game, but a lot of it autoscrolls and there’s unusual fantasy vocab all the time. This is another one you can probably beat even if you don’t understand all the text, since it’s classic 3D Zelda formula.
Oh, and if you have an international N64, you can actually play Japanese N64 games with no issues, the only ‘region locking’ is the shape of the cartridge back. You swap the back panel from any international N64 game onto the JP game and it’ll fit and run just fine.
ゼルダの伝説スカイウォードソードHD (Zelda: Skyward Sword HD), Switch, 2021 (original was 2011) -- L27?
This is another Zelda game, but it has more text than OoT. It has a kind of hard to read font, but there’s furigana everywhere so it’s not too bad. Only a little bit of hard vocab in this one, and once you learn it, the same terms get reused all the time. Not much autoscrolling.
Stray, PC, 2022 -- L27?
Cat Game! This one wasn’t in JP originally, and the translation feels a little strange sometimes, but it wasn’t too challenging. Text is also mostly divorced from the gameplay, so you could probably complete the game even if you don’t understand a lot of the text. There is a lot of text though, and it occasionally auto-scrolls
ゼノブレイド３ (Xenoblade Chronicles 3), Switch, 2022 -- L30?
I’m a big fan of the first game, and played both XC 1 and 2 in English, but decided to hop to JP for this one. I’d rank this game below 1 but far above 2 in terms of story, but I’ll spare you all the details of my Xenoblade opinions It has lots of complex vocab, complex systems you’ll need to read in-game tutorials to understand, autoscrolling text (mostly in cutscenes, but there’s some non-voice-acted autoscroll text too ), and it’s just really long, so I’m giving it a high difficulty rating.
大神 絶景版 (Okami HD), Switch, 2018 (original was 2006) -- L36?
This is my favorite game, I’ve played it probably 10 times in English, so I know the story and characters by heart. Despite that, it was still really confusing, and I totally lost track of the dialogue at times. Particularly when brush gods or other ancient beings are involved in a conversation, the language is filled with archaic speech patterns and fancy yojijukugo, so I spent ages looking up words during those sections. A lot of the older terms and idioms aren’t in jmdict either, so I was forced to use J-J dictionaries or just google them. I watched a 実況 of the game on NicoNico after finishing it and found out that I missed a ton of small jokes in the text, but was also reassured that at least a few of the most unusual terms were hard for a native Japanese speaker to read, too.
Some other ones
I played ゼルダ無双：厄災の黙示録 (Hyrule Warriors: Age of Calamity) in JP, but to be honest I barely even read the text in this one while playing, so I couldn’t tell you how difficult it is.
I’ve also played some 原神 (Genshin Impact) in Japanese, and it has remarkably complicated language. Especially the area based on China has a lot of Chinese words brought directly into the JP version, but even dialogue isn’t afraid to use rare terms or weird speech patterns, and there’s no furigana anywhere. It’s probably one of the hardest games I’ve played language-wise (maybe like L33?), but thankfully the gameplay systems are so cookie-cutter modern open world that progressing even when I was confused was never an issue.
I just started Oneshot (World Machine Edition) too. I played the original several years ago in English, but I wanted use the new version as an excuse to experience it again, and decided to try the JP version this time. It seems like a really good translation so far. A lot of unusual vocab has appeared already and I think it would be quite confusing as a learner without prior knowledge. I might put it somewhere around L27 compared to other things in this list.
I’m looking forward to seeing other peoples’ lists! I wouldn’t be surprised if people disagree with some of my evaluations, so hopefully there’s some overlap to get more perspectives.