MX unleashed does look crazy.
So there will deffinetly be no Xbox Live play? Damn. Kind of a shame, since the Moto GP demo was such a hit and everyone loved it. Same as the ultra realistic Moto GP 2, which had a lot of depth to it, being able to fully customize the decals and colors on your bike, being able to adjust things like wheelbase, gear ratios, tires, suspension, etc, which had huge impacts on the performance of the bikes. All fully lisenced bikes and everything from the mgp season.
720p deffinetly is going to kick ass with the Xbox version. Don't know why its not on the cube though.
I hope the engine noises are good. One thing that pissed me off with many of the other MX games, the engine noises are usually crap. Expecially MX superfly! Hopefully this game turns out to be awesome like Excite Bike 64 on the N64. That game was amazing, and had awesome engine noises :)