Excellent, and numerous, demos that run on very specific hardware. When you watched an Amiga demo, you knew it ran on the same 68000, graphic chipset, sound, etc. (And then later AGA machines, of course) But the typical Amiga demo didn't require VGA, or 50 mhz, or some new sound card etc etc that always seemed to cheapen PC demos. Code a demo that looks like crap? Just require better hardware. Can't do that (so much) on the Amiga.
Only thing comparable to today would be console demos, and those don't seem so plentiful, or as good, as the Amiga. (I could be wrong about that one.. I've never been one to collect, say, SNES demos or whatever.. Only recently checked out demos on the PSP, and there's only like 12 once you remove ports..)