Piper said:
V Rising is a fun game! You can make your own private server and tweak the settings to make it as easy or hard as you like.
It’s not really couch co-op though, unfortunately.
Enter the Gungeon is a top-down, solo or co-op bullet storm game. It’s fun with lots of characters, and there’s a sequel too, though I can’t remember the name right now.
Hollis said:
Enter the Gungeon is a top-down, solo or co-op bullet storm game. It’s fun with lots of characters, and there’s a sequel too, though I can’t remember the name right now.
When I finally beat the game, I opened the big chest and found the gun that solved all my problems! 
Senior officer?
How to Survive 2?
Overcooked! It’s a fun couch co-op cooking game.
If you’re looking for a challenge and don’t mind losing everything, Don’t Starve Together was a blast with my wife. We survived a year once!
Finch said:
If you’re looking for a challenge and don’t mind losing everything, Don’t Starve Together was a blast with my wife. We survived a year once!
Haha, we finished that too! Looking at all these suggestions, I realize we’ve played too many games!
Heavenly Bodies is a great couch co-op game. It’s just two astronauts trying to fix a space station. The controls are simple, but the movement is tricky. It’s short, but a lot of fun!
Wren said:
Heavenly Bodies is a great couch co-op game. It’s just two astronauts trying to fix a space station. The controls are simple, but the movement is tricky. It’s short, but a lot of fun!
Thanks for the suggestion! That sounds interesting!
Try Conan Exiles, Valheim, or Survivalist: Invisible Strain. None of these are couch co-op, but they’re all great online games. The first two let you run your own servers and mod them.
State of Decay 2 is another fun one.
Enshrouded is another good game.
Outer Wilds is a great game too.
My husband and I loved Ark, Call of Duty, DayZ, and The Quarry. We also took turns playing Resident Evil and the Dark Pictures Anthology. Right now, we play World of Warcraft and Once Human together. Once Human is a zombie survival game with building and taming.
Don’t Starve Together.
It Takes Two is one of the best couch co-op games ever made. Give it a try if you haven’t already.
Wei said:
It Takes Two is one of the best couch co-op games ever made. Give it a try if you haven’t already.
Oops, I feel dumb! I didn’t read your post properly. My bad 
Wei said:
It Takes Two is one of the best couch co-op games ever made. Give it a try if you haven’t already.
If you liked It Takes Two, check out Unravel 2. It’s similar but a bit more chill and relaxing.
@Laine
Already finished it too!