Have been really enjoying Brogue lately. Besides the difficult, turn-based gameplay (decision making is more cerebral than reactive), I think ASCII graphics are part of what makes these games so enrapturing. Our brains are incredible at constructing rich narratives from limited information.
Brogue is genuinely beautiful. I know pure roguelikes should be white ascii on black, but it's incredible what a little color can do. And the way it handles dynamic events in its environments. Really makes the cave "biome" come alive.
Even the original Rogue had color and graphical tiles as soon as it was ported to systems that supported them. I'm sure there are people out there who think "true" roguelikes have to be monochrome but I'm lucky to never have met them.