I'd say for OCS in order of awesomeness (just off the top of my head)
Mega Typhoon (actually requires ECS, to fit some HUGE buffers, supposedly.)
Shadow of the Beast series
The 3D poly department was a bit dire, perhaps because it was easier to write cross-platform versions, but some prime examples are
Now, most of these games above were selected for code speed, but f.ex. SoTB looked cool more from the parallax, number of colors, big objects, etc. There are other things that make games "not look ancient" or be impressive/arcady these days, regardless of how much pressure was put on the CPU
The Pinball series, for example, still good looking and a finely tuned game experience. Amnios has some cracking graphics as well as the Bitmap Bros games and some excellent games from Graftgold, some of these will play less well or look slightly less impressive today due to the framerate. Lotus series still look quite okay to my eye also
There's also the sound to think about. Pinball series had very well produced sound effects, and many many games had better music than any other platform for years.
I'm trying to think of some games with really immersive sound effects and maybe context sensitive 'event' music, but maybe you can help add some more games on this note.