If you are primarily a PC gamer, like myself, then you've mournfully watched the releases of Guitar Hero and Rock Band float past (I am going to ignore the PC port for GH3, since it does not bear any recognition). We've always know that the PC is, in some ways, the ideal platform for such games, owing to the long history of user created content. The PC certainly lacks the social aspect that is one of the primary draws of the game, but that is changing as consoles become more like PCs and PCs adopt some of the ease of use that draws us to consoles.
Audiosurf is, in many ways, exactly the reason that the PC could be the best platform for rhythm based music games. You can play the game to any song in your library (barring songs with drm, but that's hardly the game's fault, yeah I'm looking at you ITunes, and don't think you're off the hook Napster et al.). Audiosurf takes any music file you enter into it and procedurally generates a course that you can traverse in a hovercar, dodging or picking up different colored blocks to score points by matching blocks of the same color together. The gameplay can be as relaxing or as intense as your mood dictates, depending on the tempo of the song you choose. I get an entirely different experience from Moonlight Sonata then I do from Mars Volta's Inertiatic E.S.P.
The nearly endless replayability, as deep as your playlist and as wide as the many different modes of play that the game offers is driven further by the global scorekeeping for each song (though it relies on proper naming of the song). Not all songs translate well into the medium, as many are too slow and some are too irregular, or too complicated (many classical songs seem to have too many layers for the system to pick out specific instruments to map). The result is that listening to your music elsewhere, in the car or on the bus, you pay attention to the tempo of songs, and mentally flag ones that would work well in the system.
The graphics of the game are abstract and exciting, colorful and random, with smoothly curving translucent tracks and beautifully simple cars. There is enough in the background to keep it from simply being empty space, but not enough to distract the eye. Everything, from the track to the background to the movements of the car, is synced up with the song. It's a playable visualization.
The simplicity of the game means that anyone that has music and can move a mouse can pick up the game and try it. Any computer could run it, and even on low settings it looks beautiful. The low barrier of entry puts this on the forefront of my personal movement to widen the understanding of gaming in the public perception, alongside Peggle. Tell your ma, tell your pa, have your non gamer friends over and tell them to bring their music. This is why we game.