You can't use a standard DVD to calibrate the display for games sent in HD, but obviously it will work great for DVDs. They just aren't the same (DVD being 480i, games being 720p or 1080i, and the differences in the signals are much more than just resolution). Generally it seems you need a much lower brightness setting for DVDs than for HD stuff, for starters. Of course, if you're playing games at 480p, then the calibration should carry over from DVD.
Some of the EA Sports games have very good calibration test patterns, the best and most complete I've seen in any game, though a few others do have some sort of pattenr to set your contrast/brightness settings. NHL07 is the one that I have (I think NBA Live has these patterns as well, but neither of the football games do), and it includes a nice brightness test pattern, complete with gradation scales and a blacker-than-black drop-shadow thing, as well as standard SMPTE color bars so you can adjust your color and tint if you have the filters from DVE.
It is also possible that you can stream HD test patterns from your PC through the 360's video player, although I'm not convinced that this will exactly match what the games' test patterns give you. It seems to me I have to adjust my black level between HD video and games (though it's only a couple points, and I don't yet have an ideal HD test pattern to stream). I'm not convinced that all games adhere to any standard calibration, either, but you'd have to think the games that include a test pattern or two have been made with that calibration.
Once I get the HD-DVD drive, I will really want the HD-DVD version of DVE, but I'm not even sure if that's been released yet.