Games aimed at kids tend to rely on hiragana, which can be fairly slow and confusing to read and won't give you kanji practice, so I wouldn't necessarily call it great for learning. However, you will get a lot of katakana practice, much more so than games for adults, at least in my experience.
Take Paper Mario: The Thousand-Year Door here. Loads of characters use katakana intermittently, but all speech from this sentient supercomputer will be entirely delivered in katakana (except for 世界 and 見 for some reason). It's a cool way to communicate that the computer has a unique speech pattern, but it's also great practice if you (like me) are not that good at reading katakana naturally. This particular conversation goes on for a very long time (at least at my speed) and it sounds like I'm gonna be having more conversations with it going forward, so there's a lot of katakana to sink your teeth into in this game.
Similarly, I recently finished the Super Mario RPG remake for Nintendo Switch. Slightly more kanji in this than Paper Mario, which was nice, but still not much overall and still a lot of katakana. There's an entire village of people that are meant to be mind-controlled, so they all talk exclusively in katakana. I love getting practice, but my god, the relief I felt when they went back to speaking in hiragana. It's also nice that conversations in this game tend to be much shorter than Paper Mario since this was originally a SNES game.
I've also been playing a few games that are aimed for older audiences and yeah, purely in terms of katakana practice, there's no contest. If you find yourself struggling with katakana, I recommend picking up a game for kids.
by Big_Description538