Rez is a game that makes me wonder, just how easily amused am I anyway? I agree that the gameplay is rather dull, but somehow it just... doesn't... matter. "Mesmerizing" really is the best word to describe it.
Seriously, I should be able to fully recreate the Rez experience by merely using a cool Winamp/Media Player visual plugin while blaring some techno at top volume for forty minutes. Somehow, that just isn't the same as playing the game.
And the fourth boss monster is one of my favorite moments in all of gaming. Everything feels like it's going at 500,000 miles per hour, the already awesome soundtrack is absolutely at its best here, and I love the way the enemy divides its time between assuming a human form and splitting into hundreds of spinning fragments and add to the sense of pure chaos. If only that boss were actually as deadly as it looked...
My biggest problem with Rez is that $50 struck me as an insane price to pay for it. For the longest time I couldn't even find a used copy that was priced below $40, and the game's just too weak and waaaaaay too short to be worth that much IMO.