Making a playlist for a newbie

So I have this friend who I would like to introduce to Dream Theater (he's heard OF them, but couldn't name a song). He's an older guy, probably the biggest Led Zeppelin fan you'd ever meet.

If you have 60 minutes of time to introduce someone to Dream Theater, and try and show how diverse their collection is, what songs would be must haves?

Will be listening through Spotify, so basically anything in their catalog there is available. I was tempted to just say "all of Images and Words" or "all of SFAM", but I wanted to vary it up a bit.