[Steuard]

I've always had the impression that Nethack had pretty much the best attention to detail of any roguelike game, and the most thoroughly developed game world (though much of that only becomes apparent about halfway through the game). Rogue clearly would have been a great choice from a historical standpoint, but I can't argue with their choice that Nethack is pretty amazing as a work of art. (I can't comment on DCSS.)

[kibwen]

It depends on how you define "attention to detail". Both NetHack and DCSS feature online play and fiendish difficulty. NetHack's claim to fame is its complex system of interactions and "the devteam thinks of everything"[1].

On the other hand, DCSS is the pinnacle of roguelike usability. The devs strive to make the game "fair"--which is to say, a death is (99.9% of the time) your fault, and not just bad luck. So no instadeaths, no save-or-die effects, and spoilers should be largely unnecessary (that's the philosophy, at least...). They also hold annual usability studies and incorporate that feedback into the game. As a result, it's a game that's both very approachable and very deep. I highly recommend it if you're a fan of roguelikes.

[1] http://nethack.wikia.com/wiki/The_DevTeam_Thinks_Of_Everythi...