REZ for Dreamcast
This game has got to be the best game ever created. Granted, its graphics are largely wire-frame and simple polygons, but its not that, its how its presented. The game is all vector based wire-frames with transparency of texture over them. The enemies are a combination of wire-frame and single color shades per side. Your character can level up and change forms, becoming more powerful as you go. Everything you do creates music in the game; putting your crosshair on an enemy, firing, and destryoing them too. Most everything in the game acts as a living visualization for the music; buildings pulse, roads are waveforms, and your character pulses too. Events are also timed to the music (which is a very intriquieing club mix) so thats really cool too. Visually its simple, but the game just immerses you in its universe of colors and great music and sounds. Ill post some screens (though they do it no justice) here.