BG1+2: Those games had several dark places, but also many places that were not so dark.
Many characters were completely over the top cartoony crazy: Minsc talks with his hamster, Jan Jansen talks nonsense all the time, Xzar and Montaron are paranoid psycho killers, Xan is whining all the time, and so on.
Most of these characters are so memorable because they are nuts.
Lots look at Larian:
In D:OS1 your main quest is to investigate a cult that sacrifices people to bring the end of the world. There are several areas with piles of corpses and blood all over the place.
In D:OS2 you start in a prison were they turn prisoners to mindless zombies. Later you come to many places that are destroyed, overrun by void monsters or demons or different groups of people are busy killing each other. Your ability to talk with ghosts is useful because there are so many corpses, even if you do not kill them yourself.
Sure, both games had also some over the top funny things.
The Preview of BG3 showed a soldier being turned into a tentacle monster and the intro movie shows the destruction of a town and people being kidnapped and infected with a parasite by such a tentacle beast. very funny and cartoony, right?
my opinion: BG1+2 and and D:OS 1+2 are actually quite similar. both have some dark places, some not so dark places and some over the top crazy characters.
I think the main difference is, that BG1+2 had painted 2D backgrounds while BG3 has a detailed 3D graphic where you can look at everything from all directions and move every object.It makes a difference if you walk through a idealized picture of a place or if you walk through such a place looking from the perspective of your character.
PS:
I think PoE1 was too dark for me. In the first town the main attraction is a tree full of corpses, the main topic are children without soul, and there are several cults who sacrifice people, while the game had almost no funny stuff except some comments from Eder and Kana.
The game is good, but sometimes it felt almost depressive.
I think a game needs both dark and funny things. This is an RPG, not a splatter horror survival game.
Another good post MadScientist you and I think alike! +1 to everything you said.
One other thing I wonder about is why the use of Lighting (Torches, Lamps, Light Spells etc...) gets completely ignored in video games. Some of the fun I think is exploring a dark dungeon and having to manage\use your light sources like a torch where you can only see about 30 feet in front of you and if you have to fight holding it you cannot hold a shield. Maybe video games have more casuals who just feel thats more a pain than it is worth? I have found mods in the games like Oblivion and Skyrim to make dungeons darker where light sources are a must. I know this isn't what the thread meant by darker tone:)