Games as art... blah blah... whatever.
To me, Rez is simply a stunning arcade shooter. A perfect blending of visuals and sound. You can look at it in the context of evolution and synaesthesia, or you can obsess over getting 100% on all the totals and a perfect ending (which I've only ever achieved once in all the times I've played it).
It's a game to be played with the lights down low and the volume way, way up. It goes without saying that the wireframe and flat-shaded polygon visuals appeal to me. As far as I'm concerned this is the way games should look - the way I always imagined they would look when I was in awe watching films like Tron as a kid.
I'm tired of the debate that springs up whenever Rez is mentioned and the accusations of pretentiousness, and while I will concur that it does contain some transcendent moments and certainly has lofty themes I maintain that it's every inch a classic, supremely playable, toe-tapping, visually beautiful shooter regardless.
And the Dreamcast / Playstation 2 debate? I'll take a consistent, fast framerate over a slightly crisper audio any day.