The best game in my opinion is Halo. You will hear creatures from behind and as you turn to find them, they will pan from back to front, and left to right. It is truly spectacular. The bass is also thumping as well as all of the ambient effects. No games are made as of yet at a resolution greater than 480P. The first game that was announced as 1080i was Test Drive. It is getting closer to it's release but nothing has been mentioned about 1080i.
If you want to make a believer out of a skeptic who doensn't think high quality sound makes a difference in a video game, put in Halo and crank up the volume when a covenant drop ship is landing nearby. This game has a higher quality sound production than most feature films.
I also vote for Halo. Halo's sound is good because it is subtle when it should be, unlike so many other Xbox game's audio where you hear things in the surround channel that shouldn't be there. There are times, though, when something behind you will scare the crap out of you. Lots of times. Also, the quality is very good, as walter mentioned.
I'm not sure if the fact that Halo has a pretty quiet center channel is a bad thing. Most things, be they videogames or DVD's or whatever other type of surround encoded media, rely so much on the center channel that it kind of overwhelms all the other channels, somewhat muting the surround effect. I know that technicaly 5.1 should be superior, but it sure doesn't hamper Halo's audio impact to me. PGR has a quiet center channel too, but the sound still seems pretty well anchored to whatever channel should be most active, depending on the on-screen action.
Thanks for the responses guys. Well I finally took the plunge and went out and bought some cheap RCA/BNC connectors and ran the xbox through the Quadscan. I hesitated hooking up the xbox to my HT system because I thought it wouldn't work. Well, boy was I wrong.
Halo sounded awesome. You guys were right. Only thing was that my motion sickness was intensified 10-fold on my screen. PGR really rumbled but I was a little disappointed by thee lack of surrounds and the stretched out look on a 16:9 screen. Though it did remind me scenes out of Ronin. COuldn't hear the CPU cars rolling up on me as much as I hoped, though. DOA 3 looked absolutely awesome. Best graphics. The blue sky in the beach stage was impressive.
Surprisingly, NHL Hitz was my favorite for a couple reasons. SOund was only ok. The players were a little jaggie on the edges but the ice looked awesome. Soooo clean. Also the options allowed me to take off all the static images that posed threats to my CRT. It's a pitty that game designers don't allow this more often.