My partner and I make a point to occasionally play through a couch co-op game as well. Here are some of the things we enjoyed.

Phogs - Currently playing this. It's a cute, dog-themed puzzle game thing, where you play as two heads of a single long dog-thing. We're enjoying it, but we're not particularly deep in, and I do wonder if it'll get Ibb and Obb samey, but it's worth checking out imo.

Cassette Beasts - Couch co-op, Pokemon inspired, adventure RPG with great storytelling, fantastic music and a retro aesthetic. The world is very Zelda-like in exploration and puzzle solving, while combat is Pokemon double battles. Highly recommended, just be aware that one player gets to be the player-made protagonist, while the other is one of an interchangeable series of partner characters.

Sea of Stars - The co-op update did a lot of good for this game. A Chrono Trigger inspired, faux-SNES era, indie RPG. There's a lot of unvoiced dialogue, which I could see as being a barrier to enjoyment as a multiplayer game, but the game is paced quite well, so I don't think it's a huge problem. Also, players do take turns inputting commands, but everyone is responsible for the timed hits/blocks, and you each control a character of equal agency in the overworld, so it avoids the largest co-op turn based RPG folly of having one player and one half-watching "follower." There are a ton of accessibility options/features (difficulty is VERY malleable), and as an added bonus, there's a free story DLC coming on the 20th.

Children of Morta - This is perhaps the most "hardcore" of my list, but the girlfriend, despite explicitly not enjoying "hard" games, really really enjoyed this one. An action-RPG with some very light roguelike elements, Children of Morta has you play as a family of hunter-gatherer-warrior types in a fantasy world, working together to stop a malevolent power from corrupting the physical world. Each family member has a different playstyle, their own skill tree, and a lot of personality. The game is very story driven, with a few moments being taken between each run for the fantastic narration to drip feed the narrative, slowly teaching you more about the world, the characters, and their family dynamic.

These are the ones that came to the top of my mind, either because they were particularly good or, in the case of Phogs, is ongoing. If I see anything else worth mentioning when I look at my Steam list next, I'll add.