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I completely disagree. The ASCII "graphics" (if you can really call them that) are a huge reason why I've never even considered playing it. I've read all about the mechanics, and they're interesting. I just don't understand why anyone would spend so much time developing so many intricate features when the presentation is so poor.
To me this is like saying you don't like books because they're black and white. With ASCII I've some textual description of what an object looks like (say, dwarf), but most of it is filled in by my imagination, and it does a much better job than any artist, and it's more dynamic, adapting to my mood and what I'm experiecing. Talk about high-tech. A tileset puts a great constraint on that. If there's a choice between…
I could spend some more time learning the DF glyphs, but a picture is worth a thousand words.
I killed the Balrog in uMoria* back in the day, so I'm not a stranger to ASCII graphics. The difference between rogue-likes and DF is the extremely huge variability in the glyphs.
Edit: To continue the comparison to books, Dwarf Fortress is like an interactive textbook, Roguelikes compare to genre fiction.
*I'm a dirty save-scummer, but I still put in a bunch of time.