I think the best CD's to impress friends with are the ones they like. Whenever a friend (mine or my wife) comes over and they show interest in the Hi-Fi, the first question asked always seems to be "how much.....". I usually respond with "it doesn't matter, would you like to hear something?". They of course bite and I set up the listening chair while they search through the CD's and records. Most friends are amazed at the record collection and the thought that "scratchy old records" sound better tham CD. Whatever they want to hear is what we listen to. We often listen to both LP and CD. I always find inner joy in the comments...."Records really do sound better than CD", "It sounds like the band is right there", "If you close your eyes.....", "the voice is so clear and clean", "I've never heard anything like this before"
Let your guest pick the music. They know what they like and what they are familiar with. THAT is how to impress them this hobby. Cheers, Doug