absolutely wonderful article... I've tried many times to play it, and I would survive all the bads and wrongs of it, but the time limit... I absolutely CAN'T work under time pressure. so at least now I know a little more of what it's actually about :) thanks!!!

Even though I am not a huge fan of Diablo or those kinds of games, I have to say Diablo and Diablo 2 nailed the gothic fantasy atmosphere better than any other game.

Titan Quest. Just turn down the brightness level!

Seriously, Julian Love from Blizzard was recently asked about the change in the graphical style and his reply was that they made the graphics brighter and more colourful so that they would make you less tired of the game with more contrasting areas.
http://www.gamer.no/artikler/98467/diablo-ii-var-feilfritt/2/ (in norwegian)

Of course there aren't any other games with the same atmosphere as the first Diablo. But I have a suggestion nonetheless.
Since you are open to old First Person Shooters, have you played Blood?
http://www.gog.com/en/gamecard/one_unit_whole_blood#s_0
If not the chances are high that you will like it. It is very atmospheric, there is a lot of attention to details, the level design is great and the monsters and weapons are really good too.

While Diablo is set in medieval fantasy world, Blood is set in an anachronistic alalgam of the time between the 1890s and the 1950s heavily inspired by modern horror movies. But it does share some of the sinister, old and eldritch. You will be fighting undead, gargoyles and hellhounds, not to mention some really insane and awesome cultists with Tommy guns and dynamite. Unlike Diablo there is a lot of dark humor in the game like the ability to kick the heads of zombies around like footballs and the main characters tendency to quote Frank Sinatra at appropriate times, like "I did it my way" when you just blew someone into smithereens.
Take a look at some Youtube videos if you are interested, just pick some where the music is included and guy recording it can keep quiet.

Other than that you could find a suitable roguelike, play some fitting music in the background and use your imagination. Instead of the parody style of Dungeons of Dredmor you could have the best graphics there is.

Have a nice trip!
"There is just one word to say, as you go down, down, down - You're gonna burn in hell!"

Great dungeon exploring music:

Diablo 1 OST
Diablo 2 OST
Torchlight OST (awesome music, too bad about the graphical style...)
Die by the Sword OST
Inade - Burning Flesh (ambient music album)
Ahasverus - Evocation (ambient music album)
Ahasverus - Foundation (ambient music album)
Karl Sanders - Saurian Meditation (melodic ambient music album, has some similarities to the Diablo Soundtrack)

Some single songs:

The Protagonist - Down There
The Protagonist - The Sick Rose
Danzig - Invocation
Svartalfheim - Night Elven
Svartalfheim - Solitary Werewolf

If you play a roguelike where also roam above not just below, these could also be of interest:

Equimanthorn - Lectionum Antiquarum (occult ambient music)
Shinjuku Thief - The Witch Hammer (some of the creepiest ambient music there is)
Shinjuku Thief - The Witch Hunter (some of the creepiest ambient music there is)
Shinjuku Thief - The Witch Haven (some of the creepiest ambient music there is)

If you have a forest area around where you live, I'd heartily reccomend to put on one of the albums from the witch trilogy on your ears and take a walk just when it is starting to get a little dark. It can be very evocative.

Does Ultima 8 fit the bill?

Great post with a lot of content. In fact Blood was the reason I joined GOG, it was my first purchase.

@TheCycoONE Underworld does.

Oh, and thanks on all the input, now just to press all the + thingies for you guys.

I was afraid of that.

I haven't played the Ultima Underworld games:
http://www.gog.com/en/gamecard/ultima_underworld_1_2

At least you go down, down and down. They should be less gothic and gritty than Diablo since they are Ultima, but they probably have other qualities.

Arx Fatalis as someone already have mentioned is a modern game inspired by the Ultima Underworld games:
http://www.gog.com/en/gamecard/arx_fatalis#s_0
I'm not sure how the atmosphere is in that one.

Sanitarium is a very good psychological horror adventure game.
If you don't mind solving problems instead of killing things it might be of interest for you: http://www.gog.com/en/gamecard/sanitarium
Think of the atmosphere in the carnival level in Blood and you have an idea of what this game has to offer. The first level here is an insane asylum and this is where you start out as a patient.

Success and progression in Super Mario Bros 3 is based on the gamer's skills and reflexes. Hence, Super Mario Bros. 3 is an action game.

Success and progression in Diablo is based on stats, i.e. the character's skills and reflexes. Hence, Diablo is an RPG.

Anyways back on topic: Heretic Kingdoms: The Inquistion.

No, Diablo is not now nor has it ever been a RPG. It's more than just stats, take Fallout, for example. Fallout has SPECIAL and traits between which everything is affected, on top of that the game has stats in the form of skills that influence more specific activities.

And it doesn't stop there, you actually go about and roleplay, you get to make decisions, with consequences.

In other words Diablo is to a genuine RPG game what a railshooter is to Quake.

Right. An RPG, at it's core, is a game where you can build the character from the ground up. This means race, sex, creed, age, attributes, profession, etc. DnD is an RPG. In DnD, you "play a role" that you've created. In Diablo, you choose a prefab "template", and choose from a limited selection of skillsets. I'd go so far as to say that Final Fantasy is even less of an RPG than it is a TBS, since character skills an attributes are automatically increased based on each character's template, and all the player has to do is grind for XP until that happens. You don't get to choose which spells are gained or whatever.

Diablo is a Hack 'n Slash, with the added fun of choosing from a branching set of skills and powers.

Don't get me wrong, I think Diablo was a really fun Hack 'n Slash, but it is an extremely shallow RPG if you can even call it that.

Reading those articles makes me want to attempt to play it, but man...it sounds like a total mindfuck. Personally, I take those types of experiences in stride fairly well? However, usually in the realms of movies, or books. Which brings me to my next point, from reading all three parts of those articles, Pathologic sounds like something that would work well in a literary setting, which imo, solidifies my belief that games can be art.

Has any progress been made on replacement English translations? The English version was criticized heavily for how difficult it was to understand.

If Fallout is what you define Computer Role Playing Games by I think your list will be short :-) Have the pen-and-paper role-playing ideas ever been applied in a computer game in a better way than in Fallout 1 & and 2?

There seem to be several definitions of what a CRPG is and not any real consensus. I've seen some people emphasize the role playing aspect arguing that if you role play a character you are playing a roleplaying game. I disagree with that for several reasons, one of that is that most computer games could be defines as a RPG then. And when you are not role playing at all like I think we do most of the time, just playing the game strategically are you not playing a RPG anymore?

Doady define games where success and progression is based primarily on stats as RPG which I think is fair.
The problem with that definition is that it would also include games from other genres which use stats for combat or something else even if they have no other RPG elements. While perhaps calling Action\Light RPG hybrid games RPG's have become quite accepted these days it gets more problematic if you look at other genres.

Many strategy games, especially those set in a fantasy setting use RPG elements, for example the Age of Wonders and Heroes of Might and Magic series. I would never call them RPG's though since the focus is very different. GOG actually have classified Warlords Battlecry 3 as an RPG game first and strategy game second while it very clearly is an RTS with RPG elements:
http://www.gog.com/en/gamecard/warlords_battlecry_3
As a strategy gamer I find this use of RPG annoying.

My personal definition of a CRPG is a computer game that is mainly inspired by a Pen and Paper Role Playing Game or a computer game inspired by such a computer game. Thus both Rogue, Diablo, Wizardry, Fallout, Morrowind and Dargon Age Origins 2 file under CRPG. Hybrid games where the main tradition comes from another genre does file under that genre. The problem with my definition is that you can't really quantify the RPG elements in a game, leaving it open to subjective interpretation.

I'm interested in hearing your definition hedwards, if you can flesh it out a little more.

Maybe try Chasm: The Rift? As a kid, I found that game terrifying.