Kingdoms of Amalur is actually quite nice as well. As an ARPG. A 3d one at that.

Seconding Grim Dawn. Really enjoy the game and a new expansion is coming soon.

Just play Grim Dawn already. It's the best Diablo-like on GOG!

Nothing will dethrone the king though, Path of Exile.

D4 bad.

If i'm done with my current 'Grim Dawn' run I do have to check what 'Last Epoch' is all about and maybe get serious about 'The Ascent' at least one time.

Oh. . . btw i think GoG also has 'Shadows-Awakening' in its store, though that one might be less about loot.

After that it will probably be buy all remaining DLC for Grim Dawn and continue that adventure

I recommend Chronicon Complete. Very good fast paced arpg.

https://www.gog.com/en/game/chronicon_complete

Another one just crossed my mind: The Slormancer.

But it's still in early access!

Tales of Maj'Eyal comes to mind.

If you feel you want a rouge-like experience, you can try DoomRL or DiabloRL, and many other RL experiences.

Check out Soldak Entertainment's games, then. This sort of ARPG is all they make. They're very low-budget indies, but the gameplay is quite solid (if perhaps a little unpolished). There's no real story in any of them, AFAIK, only an excuse plot and some lore (and not a ton of that).
You can also find DRM-free demos for their older titles (from before GOG started carrying demos) on their website. (Just ignore the broken "Demos" button and instead go to the page of the game whose demo you want to try.)

- Grim Dawn

Game is simply amazing. Probably the best ARPG on GOG. This game was always on the back of my mind before but I never played it. I could not understand all the praise to it as a ARPG until I decided to watch a gameplay and finally get it here on GOG. Its the best ARPG I've played and its devs still active on the community to this day; and the best: They do not treat us GOG users as second class citizens. So yay to that :P !
Be warned though that the game feels incomplete without the DLCs as some players have pointed out in the other store. Unfortunately I only learned about this after buying the normal version... Haven't finished it yet, but I enjoyed what I've seen. So if you want everything, buy the Definitive Edition or buy the normal version and if you like it, get it all.

What I really like in Grim Dawn about gameplay mechanics is that the difficulty is really well balanced imo. You can play it in higher difficulties and suffer or play on easier ones and just "enjoy the world"... Well, if you can say "enjoy" in this case because...

[ Possible spoilers below, continue reading at your will and spoiler sensitivity ]

...World building is really interesting, tense and scary. Normally in games you're trying to save the world from being destroyed.
In Grim Dawn though, the 'grim dawn' already happened and the world already has gone through the worst of it.
Basically, the evil already won, and you're a random man/woman trying to understand how everything happened, who you're, trying to rebuild the world, simply survive and maybe restore humanity to something like it was before it all happened.

- The Incredible Adventures of Van Helsing

Play the first, then the second, then the third if you will. The Final Cut version, which is one big game containing the three games story in one, breaks the story progression imo. You can get the Final Cut version because it will contain "4 games" and their complete packs. Game is huge, but fun if you enjoy hack'n'slash / arpgs.

What I really like in this game is the interaction between Van Helsing and Lady Katarina. After a while you really start to create a bound with her as a player and learn to use the game mechanics on how to create builds that focus on the synergy for both. A world full of monsters, albeit more lighthearted with a simple story (still good enough for an ARPG imo) which is good enough to have fun while it lasts.

Comparing it with Grim Dawn, its a simpler game that adds other mechanics later in the story, that is, a tower defense mini game to advance the story - but its nothing that annoying if you hate it, you can get through it easily. As explained though, the gameplay shines when you learn how to create this synergy with Lady Katarina to gain that extra advantage in battle against crowds or powerful foes. (Not necessary, as the game is not that hard). So if you don't like this aspect of the game, be warned the most of the game surrounds around this interaction.

Another vote for Grim Dawn (Titan Quest was written by the same developers so has very similar mechanics). The main difference is the background - Titan Quest starts in Mythic Ancient Greece and goes on to Ancient Egypt, Babylon and China. Grim Dawn is more dark horror, world-gone-to-Lovecraftian-hell.

Space Hack is, I would suggest, competent but rather dull with fixed maps and limited loot/gameplay compared to the others. Divine Divinity is very worth considering though - very similar to Diablo in looks but with much more emphasis on quests, a good few relying on fine object manipulation. The one downside is the voiceovers sound amateurish.

Tales of Maj'Eyal is a strong contender if you want turn-based gaming and has probably the best graphics/interface of any roguelike. ADOM (Ancient Domains of Mystery) should be worth considering then also - not as good graphically (in part because the GUI is via an external program, NotEye) but it has a more complex storyline. Both games are strong on background, but with Tales this is more through the mountain of literature you find within the game.

SpaceHack is utter garbage, who binds the map rotation to the mouse wheel and makes it fixed so it cannot be rebound. Instant uninstall... but for under an Euro, it's not worth bothering with refund.

I found out I have Divine Divinity and forgot about it. I never gave it a try. Thanks.

Also I put ADOM on my wishlist. I'll try later.

The Fate series springs to mind.

Children of Morta
Darksiders Genesis
Deathtrap
Undead Horde - and probably other games from 10tons

Nox - but it's probably too old for your liking

Maybe Book of Demons, which you can request for free in the giveaway thread.