I've never played The Binding of Isaac's multiplayer, but it's an incredible game, infinitely replayable, and has full co-op now (as in you each have a full character rather than just "little brother mode")

In terms of twin stick games, Voidigo is currently giving Enter The Gungeon a run for its money.

https://www.fanatical.com/en/pick-and-mix/build-your-own-revival-bundle

i recommend this bundle, donut dodo, round guard, indie guards in that bundle,

Also Hyperparasite in this one https://www.fanatical.com/en/pick-and-mix/platinum-collection-build-your-own-bundle

Spelunky 2

Chronicon

Caveblazers

Heroes Of Hammerwatch

Helldivers 1

Barony

Terraria (of course)

Broforce

Duck Game

Don't Starve Together

Nuclear Throne (of course!!!)

Streets Of Rogue!! (keep your eye out for Streets Of Rogue 2!!!)

Wobbly Life

PlateUp

Glitchbusters

Ember Knights

Bones Cafe

Shovel Knight

Rainworld Downpour

Petal Crash

Definitely Sneaky But Not Sneaky

Sigma Impact

Cassette Beasts

Spirits Abyss

Cosmos Quickstop

DIG

Farm Together

Death Road To Canada !!!!! <-----

Knight Squad 2

One Step From Eden

Mutant Football League

Rampage Knights

Maniac (who cares it isn't co-op it is hilarious as a pass and play)

X Morph Defense

Monaco

Tricky Towers

Himno the silent melody

Dungeon Of The Endless

Adventures Of Shuggy

Renegade Ops

Omega Strikers (online team based)

Cryptark

Ms Splosion Man

Full Metal Furies

Battleblock Theater

Colt Canyon

Cook Serve Delicious series

• Castle Crashers is a classic multiplayer beat-em-up. Plays great on Proton (if that's important).
• Lost Castle is in a similar vein, though more roguelike.
• River City Girls (and sequels) is either great arcade brawler.
• Neurovoider

Great indie co-op games:

• Deep Rock Galactic. No split screen, but endlessly repayable with goals and targets in each mission. Also fun in solo.
• Caveblazers
• Guacamelee
• Tunche

Upcoming games to consider:

• Wizard of Legend 2

Broforce

Clone Drone in the Danger Zone

SpiderHeck

• Unrailed
• Overcooked

If you’ve never played Super Space ________ and you’re looking for local split screen games I highly recommend it. It’s an amazing blend of competitive and cooperative design that’s always fun and chaotic. And it’s free! But it’s not on Steam since it’s a collegiate project. Link

From what I’ve heard of Lovers in a Dangerous Spacetime, that’s a very similar game but I haven’t tried it.

If you’ve never played Super Space ________ and you’re looking for local split screen games I highly recommend it. It’s an amazing blend of competitive and cooperative design that’s always fun and chaotic. And it’s free! But it’s not on Steam since it’s a collegiate project. Link

From what I’ve heard of Lovers in a Dangerous Spacetime, that’s a very similar game but I haven’t tried it.

My partner and I like Boomerang Fu, Stick Fight, and Towerfall. I think there are a few more but can’t think of them right now. There’s not much of a goal other than competing though

If you want to test your friendship you can try 100%ing Super Bunny Man!