Here are some rough categories and hours included.

Builder / Survival

Sounded like you were not that interested in this genre but they can be fun co-op experiences.

• Terraria (850 hours) - Two of my friends I have done two clean slate full play-throughs of this game.
• Core Keeper (77 hours) - Also played through the content of this game with same 2 friends.
• Valheim (344 hours) - Did a co-op play through with a friend on this one. Might do it again with Mistlands or with other updates.

Boss Encounters / Building

• V Rising (79 hours)

Played through V Rising with a friend, co-op pve, and it was a blast. We really enjoyed the different boss battles. We are going to revisit this one soon as they dropped / are dropping new content.

Exploration / Melee Combat / Story

• Dying Light 2 (87 hours)

Enjoyed playing Dying Light 2 with a friend, playing the game turned out to a mix of playing solo and playing co-op.

Platformer

• Trine

Fox mentioned this and I'll add it as well. Fun co-op platformer with some fun story telling aspects.

MMO

• Guildwars 2

Fox also mentioned GW2 in the thread. There is a ridiculous amount of content in this game with no subscription required. Combat feedback/force has always felt weak imo but there is a massive world to explore and jumpy puzzles if you are into that (love them).

More story focused co-op

Also watching this thread as I'm curious what shows up. I haven't played many games in this area on PC.