If there's one thing that roguelikes prove, it's that graphics are secondary to gameplay. Sometimes I find myself to be a fetishist for minimalist graphics (especially when my 13-year-old cousin is drooling to me over the latest in Halo explosions), but overall I really don't care too much about how the game looks. It's more about what the game is. IVAN's graphics, for instance, felt particularly well-crafted, while the various Shiren-type roguelikes from Japan tend to look silly and tacky to me.
Then again, I remember that quasi-roguelike arena game a while back that used letters for characters, but had realistic rainfall all around in the meanwhile. To me, the self-consciousness of that choice gave an understated sense of grandeur to the experience. I guess I feel in general that graphics, when a focus, should advance the game; if they can't, then they should at least be clear and undistracting.