Well, I may be the only one who feels this way, but when it comes to adventure games, my heart still belongs to the old Infocom classics, whose graphics were formed only in my head, with a depth of detail that I've yet to see supplied by in-game graphics in any game. Too many adventures seemed in the past to assume that if they had graphics, they no longer needed to expend any real effort in the writing. Graphics are nice, but when I'm supposed to be able to recognize an object that is 5 pixels wide and 3 pixels high, that goes beyond merely bordering on the absurd.
As for the Infocom titles, picking any one is difficult, but of those I've completed, I'd probably say I enjoyed Planetfall the most, followed closely by Hitchhiker's Guide to the Galaxy. I would perhaps reverse the order were it not for the fact that at one point in HHGTTG, the game simply lied to me. I have of course forgiven it but will ... <sniff> ... never forget the slight.
I'd include a screen shot, but that would be utterly boring I'm afraid, as it would look pretty much like the rest of this post (if you omit the smiley).