LSD: Dream Emulator (Playstation, 1998)

LSD (short for Lovely Sweet Dream, not the drug) is more about what you are seeing than what you are experiencing.  Based on the dream journal of Hiroko Nishikawa, the game takes place in those scenarios which came to him in his sleep.  There are no goals, no obstacles, and no ending.  You navigate through the dream in a first person view, and if you touch anything, you are randomly sent to another part of the dream, and it will become increasingly strange as you progress.
Video games are not only a visual medium, they are an interactive medium.  LSD mostly betrays interactivity in favor of visuals.  You are essentially a passenger in your own dream, wandering from one strange location to another, much like an actual dream.  Every image in the game is creative, bizarre, and slightly unsettling (or highly unsettling) and it is hard to talk about this game in terms of the concrete.  One must instead describe instances in its whole.
The game is designed to be wholly random.  You will be placed in any location in the dream, and the textures and inhabitants of the dream change every time.  In one location, you may be on a bridge in a formless void, and the bridge leads (on either side) into the mouth of a giant mask with Japanese characters covering it.  In another part of the dream, you will be in a tight hallway, and a giant face will emerge from the wall.  In another part, you will walk around a dark town, with Japanese houses concealing dim corners, and a giant geisha girl will float over your head and away into the darkness.
The visuals of this game inspire beauty, wonder, fear, and awe, sometimes all at once.  Consider the dream where you are under a highway bridge at night, with nothing in sight but a faint light.  Cautiously approaching the light, you find that it is a streetlight, and there is a body hanging from a noose tied to it.  Typical horror games will throw constant jump scares at you, without taking the time for buildup of tension or suspense.  LSD isn't even a horror game and it inspires more fear and dread in its players than most.
This game reminds me a lot of the 1929 silent short film "Un Chien Andelou," by Salvador Dali and Luis Bunuel.  That film was a series of dreams that were not held together by a congruent plot or characters, which to the average viewer, probably sounds awful, but it is actually one of the best visual experiences of the silent cinema.  That's what LSD is like.  The game brings to you into a dream-like state, where you can only marvel at its beauty, impossible to describe in the confines of waking reality.  Its removal from logic is its strongest asset.