Hmm... games never released...
Well, I bought a whole big pile of Amiga magazines so got to see reviews of a lot of upcoming games which apparently got the axe either before being released or at least after a demo came out. Some of the demo's were still cool to play.
I do believe Putty Squad came out, I seem to recall playing it.
I recall that Team17 were working on some kind of kinda top-view game, something to do with Knights in medieval times - Knights and Merchants?. It looked very nice but I never saw it. There were many games with beautiful graphics and screenshots but I never saw them surface, ever.
Some of them have been mentioned already .. .magic carpet was gunna be so cool. Infero, TFX (not a big sim fan tho)
etc
There were some psygnosis games that previewed but never arose. Something like "Pinky" which was hyped as being the next big amazing thing, never saw the light of day - looked like a trippy platform game.
I wonder if any of those game resources, source code, graphics and so on are still existence, and whether people would want to try to get hold of that stuff to continue development? I think THAT is the big question here.