Grim Dawn, with a considerable lead over all others. The reasons are many: Great build diversity, good art style, good story, great lore, awesome world. DRM-free, good music. Online-playble (optionally). Good developers and updates. Did I mention great build diversity?!? The pacing is great (though the latest expansion, Forgotten Gods significantly damaged this if you use the movement skill augments). Every foe feels present rather than just melting waves (unless you go back in difficulty). It has some rough edges (mainly UI and conveniences), but they've gotten fewer as the game's progressed.
My 2nd best would probably be the original:
Diablo 1. The feel, everything about it gets the feel right. Scary. Game play that added to that element (see: spitter monsters.)
I'm thoroughly enjoying
Book of Demons right now (an homage to Diablo 1), and it's pretty good. I love its take on gear-skills-items being all treated the same. It's an interesting twist. While it's a light game, it's good fun.
I hated
Dungeon Siege. It was bland as fuck, unfun. I hate "use based" progression in games (sorry, dtgreene), and the world was just so void and uninspired. I played
Torchlight 1 once through and found it to be much like Blizzard had already become by that time: a well-polished turd. It was so finely balanced, so "perfect" that it was boring, dull, and devoid of charm or fun. (It also was unplayble without respec mods, but I'll give it that as a relic of its time.) I never did get to
TL2, since, by the time it came out DRM-free, I had other gaming interests.
I have the
Van Helsing/
Victor Vran games in my library, and might get to them some day. As for Titan Quest -- I enjoyed it once (plus original expansion), but its pacing was off with long periods of empty walking, and too slow upgrades, and excessively imbalanced choices between the different "classes". I liked the lore and monster design though.
POE and D3 can't be included in a list. They're not games. They're online storefront services that take the disguise of a game.
EDIT: I didn't include my short appraisal of
Diablo 2. I enjoyed it, but not as much as many others. The game got wrecked by a few bad decisions: excessive death penalties for XP, EXTREME XP costs to level (because of having the ladder...), all those "closed" only features (because of having the closed online play...). Basically, I regularly gave up sometime in Act 2 Nightmare, which is when it truly became "rush to next boss, repeat, rush to next boss, repeat". The game was better before "skill synergies" significantly eliminated builds (doubly so when sorcereress' lightning mastery was made to clone fires' rather than reducing mana cost of spells to make up for the damage range/recast needs). And then runewords broke it even more with a lot of characters becoming very same-y based on them. Oh, and monster immunities wrecked the game even more making a few narrow builds necessary.
I never played
Nox when it was new-ish, and, when I tried to go back to it, I couldn't get into it from dated UX issues. Maybe I'll try again sometime.