Which Multiplayer RPG Should You Play with Friends?

Can't go wrong with any of these games:

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Dungeons of Sundaria has splitscreen and online co-op for 1-4. The game allows you to play as a Mage, Rogue, Ranger, Warrior, or Cleric.

All characters have some sort of healing capability but the Cleric has a self heal + group heal + revive. They have decent ranged damage, a good AoE deployable at higher level, and strong defense.

The mage is your traditional spellcaster, with a good mix of single target and AoE damage. Ironically the mage has the ability to take on the role of tank in a duo with another non-Warrior class. This is because the mage can summon a clone that draws enemies towards it, distracting and luring enemies away from your party.

The rogue has heavy single target damage, a decent self heal, stealth, and the ability to drop aggro.

Warrior is essentially melee/close range only. They can go 1h+shield, dual wield if I'm not mistaken, or 2h. Different abilities for each set up. They have the heaviest self healing with a instant self heal and a heal on attack. They can also aggro enemies. Best defense.

Ranger has the best single target and ranged damage end game but starts off very weak early on.

Cleric and Mage are the most well rounded characters but you can easily play through the full game with any 1 or 2+ combo of classes. One caveat is that the final dungeon will be VERY difficult on the HARDEST difficulty setting without a Warrior. But the game has 3 difficulty levels for each Dungeon. Difficult determines the amount of EXP you get, quality of armor drops, and rarity of crafting resources (used to make generic gear or class specific armor/weapon sets).

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Coridden is another great option! You have a fully customizable class system so you can easily be a DMG mage of various types or even a summoner mage or healer mage. Your friend can be a stealth melee fighter or stealthy ranger. Lots of options since you can have 3 active skill trees at any one given time (and easily switch whenever in town). There is also a cool summoning pet system with mounted combat. On top of that there is a shapeshifting system independent from your character class. You could be a mage of some sort for your human class but could decide to be a tanky ramox/hound/Dragolem for your shapeshift or a mage-like spitter if you want to play pure mage whether human or shapeshift. For your rogue friend there is a Panther shapeshift which has stealth so they could also go pure rogue human and shapeshift form. Shapeshifts also have sub-classes you can customize so for example the Panther could be built as a life leach attacker, or as more of a burst DMG out of stealth, AoE poison, or dash & charge type of damage.

But wait, there's more! In Coridden you also have MOUNTED SHAPESHIFTING! This means when your friend shapeshifts (and visa versa) you can mount each other's characters! If either of you add in the Captain skill tree this can be really handy because Captain gets to heal them self + their rider (or mount) in addition to boosting DMG/speed etc. 12 skill trees in total and at least 4 of them can summon pets that fight and can be mounted. Healer, Captain, and Summoner are 3 of those 4 with pets.

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Portal Knights is a base builder game from the team behind Enshrouded. It has Minecraft like building but more RPG elements including unique classes (Rogue, Mage, Warrior, Ranger, Druid). Mage is fun but honestly I'd recommend Druid + Rogue. The Druid is essentially a hybrid that can heal/tank/melee/magic. They can use all the Mage's spells and have access to shapeshift into different creatures with different fighting styles and utility. Bear is defensive, flower best has ranged DMG + heals, spiders have mobility (sun spiders can heal), gazer/bat can shoot chain lightning and glide, slimes have AoE damage, etc. It's one of my favorite base builders. Played through it multiple times which I normally will not do with a game.

As a co-op connoisseur I can't skip this question:

• TrinityS - a short experience inspired by FFXIV (and other tab-based MMOs), with full focus on raiding. Everyone's job is distinctly different and everyone has to do their respective tasks. Top-down combat with an "autoattack" system based around AFKing that feels unintuitive at first (your abilities power up the longer you stand still, so you want to not move unless you absolutely have to).
• Granblue Fantasy Relink - a singleplayer story followed by a looot of multiplayer content (about 4x as much). Every character has unique mechanics, which should count as "classes" in a way. Gameplay is arena combat best compared to something like Monster Hunter about as co-op as you make it be, as the characters range from "I don't care what you do I punch the enemy" to "Get in my bubble for protection".
• WH40k Darktide - someone else mentioned it but I have to double down. It's easily one of my all-time favourite games. Unique classes, heart-pounding excitement from start to finish. Mission-based horde shooter. They've got the intense first person combat down to an art.
• Ravenswatch - a roguelike, and more top-down. Again, not class-based, instead characters-based (but they have distinct roles in a team). Your wish for a melee/ranged should be fulfilled with Romeo & Juliet, the newest characters added who are fully co-op focused with interacting abilities.
• Remnant: From The Ashes and its sequel - "American Dark Souls" - the traditional Dark Souls gameplay mixed with fancy gunplay, and of course, classes. Different players can specialize in different roles in the team.
• Wayfinder - not-an-MMO. A game that was originally meant to be an MMO, ran out of budget, and the devs took what they had and downscaled it into a local game instead. It's got all the good of an action MMO (classes, combat, etc), and everyone in your party can specialize in different responsibilities and roles.
• Lastly... Did you consider MMOs? Something like FFXIV or WoW might just be what you want.

I feel like co-op games are the truly forgotten kind. It's all a shit-slinging fest between singleplayer gamers and PvP multiplayer gamers complaining about eachother, with co-op just left behind forgotten and abandoned...

What system? How many friends? Can you be more specific than "RPG?" ARPG? CRPG? Action/adventure? MMO? 3D/isometric/pixel graphics? More combat or story focused? New or retro?

Dark Souls 1-3 & Elden Ring are the GOAT, with Nioh 1 & 2 coming very close.

Outward is great, if you don't mind tedious inventory management & a lot of backtracking with no fast travel. But there are lots of great mods that drastically improve the experience and even one that increases the # of people you can play with, if you're on PC. But it's a very aesthetically pleasing & colorful game with difficult but rewarding combat, dungeon exploring, looting & a refreshing take on class building.

Chronicon & Heroes of Hammerwatch are very fun dungeon crawlers with RPG elements (i.e. classes, builds, playstyle freedom, etc) if you're on PC. Chronicon is definitely loot intensive though.

I'm honestly not too big on the isometric ARPGs like Diablo, Baldur's etc, but I found Grim Dawn quite enjoyable. Yet another loot heavy PC game.

I wasn't too big of a fan of the Monster Hunter games tbh, but you might enjoy them. I can see why they're so loved and they have a lot going for them. But idk. The combat was just a bit too tedious imo, with these huge monsters attacking nonstop every 2 seconds and almost never slowing down enough, especially for the slow weapons. And it's EXTREMELY grindy. Be prepared to fight every monster hundreds of times to hopefully have a 2% chance of them dropping the stuff you need for their set. And there are just way too many items and stuff to do.