My favourite co-op games are:

• A way out
• It takes two
• Slit fiction
• Unravel 2
• Untitled goose game
• Operation tango
• Deep rock galactic

N+ for the xbone is pretty good. It's very simple but addictive.

If you can emulate get Mashed: Fully loaded for the PS2

I used to play some monkey game at uni but we were always stoned so I can't remember exactly. Mebbies it's something like Monkey ball tennis? There was loads of games within

Lots of great options here already. I don’t see Larian’s Baldurs Gate 3 and Divinity Original Sin 2 here.

The screen gets a bit cramped in co-op but it’s perfectly playable and loads of fun playing these masterpiece RPGs on a couch with a significant other or a friend.

Call to Arms: Gates of Hell

A jewel we've found recently. It's incredibly fun and vast

Where is Raft in these lists?

Spelunky2 is good, up to 4 players.

Very hard but definitely worth persevering with.

Quake and Quake 2 have a bunch of co-op modes and they have been updated for crossplay on modern systems. I was just running some of the newer map packs with my buddies last night. Quake is $4 on Humble right now.

New classic Doom versions have very good split screen options

Personally i like Duck Game for parties of 4+

I posted a review here earlier this year, but A Way Out was an excellent 2-player co-op game! I really enjoyed it. Story rich puzzles with some action interspersed. And it's split-screen even if you're playing online, so you can see what your partner is up to and coordinate with them. The ending was heart-wrenching too! Such an emotionally impacting story. Check out my review for a spoiler-free intro to that game.

Brothers: A Tale of Two Sons - pretty cool as you can play on 1 controller.
Star Wars Battlefront 2 (OG) - have awesome memories with it.
Earth Defence Force 4 or 5 - over the top bug extermination and built in split screen even on PC.
Last thing I can recommend is Saints Row 2, 3 and 4 (especially 3) - but you need something like Nucleus to play on the same device.

I really enjoyed Console minecraft with my sister and friends growing up. Play the Wii U version (with CEMU) and get a ROM and you're set.

Alternatively, can't go wrong with early Lego Games. They're basic and simple, but some of the most basic fun you can have too with another person.

Project Zomboid is also great for Co-Op. The controller controls are a little iffy depending on who you ask, but i like them.

My 1 seed for the PS2 is Cookies and Cream. It’s a split screen co-op game for 2 players where each side will have obstacles that only the other side can solve. Very fun and very addictive, but it also has a solid control scheme that is easy to pick up.

My wife and I played it a lot when we were first dating and she loved it even though she rarely, if ever, plays video games. Still have the original copy and I’ll never part with it 😊

Look up tiny best set go on archive org. Lots of games in that one