For discrete surround demos, yeah, agree that DTS demo discs are great for those.
There's another type of surround-sound demo, which for me is even more impressive. That's when all speakers, including surrounds, work together to create a coherent soundfield or a "bubble of sound" or whatever else it's called.
Examples (possible spoilers):
- Kill Bill Vol. 2. When the bride is being buried, there's nothing on the display, there's just the sound. And it will sound like you're inside the coffin, and the guy is shoveling dirt on top of your room (i.e. on your ceiling just above your head). So it feels like it's you who's being buried alive. Spooky.
- Requiem for a Dream. There's a scene where you're immersed in the middle of a drug-induced trip, complete with hallucinogenic sounds. IIRC there are several such scenes. What I do remember is that this film has great sound design.
- Super Speedway. Still one of the best demos. Here, your room is the car. The front tires are rumbling away in front of you. The engine is right behind you, just like it should be. And when the car hits "the bump" it feels like your couch is the driver's seat. WHAM!
- Blue Crush. When the big wave crashes, it rolls from the front of the room, toward you, and away from you toward the back of the room. It feels like you need a towel after that.
One of the best ones that pros use for testing an entire 5.1 system is U-571. No, not the depth charge scene. The one in the dining room. I'll look it up and post again.