i have been in the scene since forever, one of the best demos of all time is eNGIMa by phenomena , state of the art is cool indeed and was cool when it came but 9fingers i liked more (hated it the first time i saw it ,due to the weird choice of music but second time i viewed it i loved it)
beyond that...lEGOland 3 on c64 is awesome.
And nerve axis RELIC is awesome...
and ofcourse dolphins dream by us in push-entertainment ...
there is way too many to mention , but demos you must check out is , Virtual dreams - factory , sumea and psycadellic .
and nexus7 from andromeda (this is ranked as maybe...number 2 on my best demos of all time on amiga) ..
and traffic by mystic has alot of awesome stuff even now , sure i know its alot of fakes in it etc , but that doesnt matter ... if only 2 parts was removed from t...then it would have been nearly perfect

i never liked ZIF , boring music etc..
Stellar - mindflow is a demo that no one should forget.
i could go on for decades about all the stuff.
i have over 50 cds here with scene stuff , 15 of em beeing demos only , rest is wild demos and most of em amiga exe based ones (huge anims) , and some very nice coded wild demos like .. TWISTED by polka bros

cheers