Oh and yes by the way they do claim that the game is in HD right on the back of the box "HDTV 720p/1080i/1080p" if you dont believe me you can look at your own case.
Halo 3 has a native resolution of 1138x640 pixels.
Minimum to be HD, like they claim on their packaging, is 1280x720 up to 1920x1080.
"Running at only 1138×640, that means there are 728,320 pixels. Thats a full 193,280 pixels LESS than 720p. In fact, it is even less pixels than your very average 1024×768! Hardly what anyone would consider high-def." - quoted from
Gamerawr!HD 1920x1080 = 2,073,600 pixels on screen
HD 1280x720 = 921,600
XGA 1024x768 = 786,432
below XGA 1138x640 = 728,320
800x600 = 480,000
I think you need to understand that the native resolution of 1138x640 pixels is only inside the frame buffers, once it goes throught the 360 output hardware its scaled to whatever you have chosen in the dash ie 720p or 1080i/p or even 640i... this is what the box means, as all you as a user need to know is that the xbox360 will display this game in thoes hd resolution.
Comparing halo3 to gears is a bit harsh, the enviroments in gears for the most part are up close and gritty whilst halo has wide open expanses which are totally different and much more taxing on the hardware. This is why the fighters in a 1 on 1 beat em up are always better than the characters dynasty warroirs say. They spend more pollys and more affects in a smaller area. I think Halo3 has a nice blend of up close detail and impressive draw distace going on, I think technically its much more advanced that its getting credit for.
This is all down to a smart move by M$ the scaler they touted allows for game designers to tweak things for over all performance, if bungie where forced to 720 you might find it would cost you 30fps... so slightly less crisp images for thoes with hd sets is much better than halving the fps for all users.....