While they don't exactly fall under the umbrella of games, I find the most solace in visual novels. I'm a person who heals best when experiencing strong emotions and nothing can achieve that quite like a good VN. I love the fictional friendships you form within them and while I'm aware they are not real, they still can make me really happy. Paired with a good backstory, nothing can comfort me as much, aside from my close real life friends.

Depending on the person, there's different types of VNs to choose from. Moeges are the typical feel good VNs, there usually is hardly any drama and they just focus on the interpersonal relationships. Most of them are a kind of advanced dating sim though, so I'm sure they are not for everyone.
Then there are Nakige, which I love very much but might be bad for most people with unstable emotions. Also called "tear jerkers", they contain quite a bit of drama and melancholy. They usually end on a happy note though.
Utsuges are like Nakiges, but even harder on the soul. They don't usually end on a happy note.
Personally, I also love horror VNs, but I guess I'm kinda a special case in that regard. I can go into them and enjoy them, even when I'm at my lowest, but I highly advise against them if you're not a hundred percent sure that the person can handle them. I've witnessed quite a few people getting drawn deeper into their holes.

As you can see, VNs tend to be quite emotional, one way or another. For me, that's exactly what I need. Maybe some of your clients can benefit from that as well. One thing might be worth mentioning though: Oftentimes, the relationships in a VN start off very rocky. If a client has some kind of trauma that might be triggered by this, I would advise against VNs.