Mijknarf: Acoustic guitar sounds outstanding on my system, too. So do jazz and chamber music. It seems the "simpler" (it terms of ensemble size), the better.
I disagree with one post saying that Leo Kottke was boring. Listen to his first album ("Six and Twelve String Guitar") and tell me, honestly, that it's boring. It's amazing. Glad to see a recommendation for the great, late-departed Michael Hedges. I personally prefer "Breakfast in the Field," but any of his are worth obtaining.
If you like the John Mclaughlin style, then "My Goals Beyond" is a must, as is his acoustic album with Santana.
I'm not sure if you were looking primarily for recordings of well-played music, or for well-recorded/engineered CDs.