The best experiences:
3dDeathChase- fast and first person.. my family was amazed with this little piece of software.
Football games - Always has been a football game which has shocked me, my brothers and my friends.. first MatchDay, then MatchDay2... but specially EmlynHughes in Speccy and KickOffs / Goal!! on Amiga.. these games were/are truly an experience because you learn tactics and control/movements even nowadays.
Also PlayerManager no other game is as involving as this masterpiece.. except Elite
Elite Braben/Bell had to be in state of grace when they created this game. Everything is conceived to let you create your own story.
Ranarama on speccy. I never got into Paradroid, but I got hooked with this variation of the game. Its gameplay system is like RPG but in a wild arcade shape.
Driver it was a cool experience when I discover it. later GTA3 truly new sensation of freedom.
Then the last notable experience has been MetalGearSolid and MetalGearSolid2. But nowadays I guess itsnt as authentic likes previous ones..