If you’re looking for something geared more introductory to co-op board games, Castle Panic is good:

https://boardgamegeek.com/boardgame/337394/castle-panic-deluxe-collection

Horrified is a great co op board game. Can mix it up a few times.

Replayability will be limited, but I’ve only played it around 4 times since owning it October 22.

Lots of great games mentioned. If you have younger ones that you want to bring in to the fold, there’s a couple good ones I’ve had success with:

• Sky Magic: you play as fantastical creatures trying to brave an oncoming storm, everyone needs to get to safety to win, so some strategizing together to optimize each other’s paths is rewarded.
• My first Castile panic: simplified version of the classic suitable for the younglings.

I prefer co-op games over others, so I love this question.

• Castle Panic
• Pandemic (with the easy difficulty level for beginners)
• Eila and Something Shiny

Coop games are tricky because many allow “quarterbacking”, which, while really being a player problem, I blame on bad game design. (For example Pandemic could really be played solo with 4 stations)

So you need coop with asymmetrical information and nobody can have all the information.

Hanabi is a great classic example of a game where nobody can see their own cards, but there is a limit to the amount of info you can give out.

Just One is a newer example of a coop party game.

Library Labyrinth recent delivered its kickstarter. The basic premise is that a bunch of evils have escaped from the books in a library, and you have to use great women from literature and history to defeat them and shove them back in their books. The first time I played it I got to say the immortal line “Mina Harker, in the library, with a photocopier!” It’s a lot of fun and pretty quick to pick up, and the production values are very high. Definitely a recommend from me

For beginner friendly co-op games I’d recommend:

• The Crew which is a trick taking card game, and has a great legacy/mission system, easy to learn
• Forbidden Island
• Burgle Bros

Magic Maze is great for newbies - rules are simple and introduced over multiple scenarios. I’ve had success with both kids and adults.

If you like word games, Illiterati is a cooperative word game. It plays a bit like Bananagrams in that you’re having to accommodate additional letters into your sets of words, and each player also has their own category of words they’re trying to complete.

Red November, Forbidden Island, and Forbidden Desert are all pretty similar “Move your pawn around and do things before everything blows up” type games similar to Pandemic.

There are lots and lots of co-op games. The former top 1 on bgg, Gloomhaven, is a co-op dungeon crawling rpg in a box.

If you prefer kicking some eldritch asses together there are all the Eldritch Horror, Arkham Horror, Mansions of Madness and Elder Sign, where you and your loved ones can go (globe/city/mansion)-trotting to beat some abominations and save the day. And if you like this cthulhu theme and card games, there is the wonderful Arkham Horror CCG which is basically the same premise, but now with deck-building and more in-depth stories.

Another incredible one is Dead of Winter where you and your friends simulate being the last humans in a colony surrounded by zombies. It can be full co-op, but the best thing of DoW is it’s hidden traitor mechanic, where someone can be working for their own goals instead of the colony.

If you like simple rules and lots of surprises I recommend Betrayal at House on the Hill which starts co-op and after the haunt of the house is revealed anything can happen. The game starts simple and ok and goes on a crescendo of twists and turns that leaves you wanting more.

And finally if you just want to sit around with people on the table and solve something together like a puzzle, I lived Sherlock Holmes Consulting Detective. A game where you and your fellows are the street boys of Baker Street helping (and in this case competing against) Sherlock to solve mysteries. It has basically no rules and everyone work together to solve the mystery as fast as possible.

I’d recommend Sentinels of the Multiverse. It’s a fun co-op card game about superheroes trying to defeat a supervillain. It can get a little expensive if you try to buy every set in the series (my friends and I have done exactly that and it’s a massive number of cards), but all the different sets are compatible with each other, so you can pick the ones you want and just get those. The core gameplay loop is pretty simple where the villain and the players all take their turns attacking, but there is a ton of variety in how all the characters can be played.

https://boardgamegeek.com/boardgame/102652/sentinels-multiverse

Did no one mention LotR: Journeys in Middle-Earth? Its a great coop game, the only con being it requires an app to play. There are few expansions that introduce more playable characters and campaigns, with standalone campaigns being purchasable via the app.