If you're trying to introduce a friend to classic rock you should start with very well-known bands and their well-known songs. Here's a few that come to mind right now. Jumpin' Jack Flash by the Rolling Stones. Rock and Roll by Led Zeppelin. Wish You Were Here by Pink Floyd. Seven Seas Of Rhye by Queen.
Here are some songs that'll bound to get your friend to like classic rock.
"Money For Nothing", by Dire Straits. It has an awesome intro guitar riff.
"La Grange", by ZZ Top. Again, the kickass intro riff.
"Highway Star", by Deep Purple. One of the best song verses ever.
"Eruption", by Van Halen. A little extreme, but it's one of the fastest guitar solo's out there.
"Voodoo Child (Slight Return)", by Jimi Hendrix. Check it out for the intro guitar solo.
For showing a newbie some classic rock, here's some great songs to start off with.
Killer Queen - Queen
Rocket Man - Elton John
School's Out - Alice Cooper
All You Need Is Love - The Beatles
Carry On My Wayward Son - Starship
Hammer To Fall - Queen
From there, you can listen to some deeper songs, like Bohemian Rhapsody, Dream ON, Hey Jude or Goodbye Yellow Brick Road. Then some more classics. You can decide. Whatever your favourite songs are then some artists you might not have listened to yet. Both of you might be bigger classic rock fans!