Games that were ahead of their time (and in what way)

[Kaunisto]

Unreal came out just before Half-Life and was similarly a shooter with more story in it than the ordinary mid-90's FPS.

Populous was something that didn't exist back then and is sadly rare still today.

And Ultima Underworld, open world 3D action-RPG with various factions to ally yourself with etc.
I was particularly impressed with how many ways there were to open doors: find a key, pick the lock, use magic to open door or you can just smash the door open by hitting it with your weapon (potentially damaging or breaking the weapon).