As this is my personal opinion, please take it with a big grain of salt - ASD's Lifeforce is the new benchmark for demo effectiveness. It is just so
beautiful.
When I first saw Farbrausch's Debris I thought it was a bit boring. After all, it's repetitive. The soundtrack is like some cheap industrial techno, and the demo itself doesn't really show off that much.... Until you realise that the whole thing is less than 200kB. An amazing feat.
There is just one experience more profound the demoscene has given me. It must have been no later than 1995 or 1996, or about the time when the Amiga and PC groups had just discovered 3D toroids, vector castles and phong shading in general. Half of the demos shown in the party had some kind of floating/rotating phongs-shaded toroid, and about a third sported a zoom-in/zoom-out view of a castle. It got pretty dull, pretty fast.
And then finally Byterapers showed off how to outdo everyone by using the same effects with better timing. On C-64. Jaw, meet floor.