I was searching and found this, old halo games were lower that “HD” or nor on 720p (lower than that),
Halo 3 and ODST were at 640p something like Sub-HD, with poorly AA (Anti-Alising)
Halo Reach was the first bungie game that was a 720p native, but AA on reach were remarkably better.
Here is the full article (it’s on spanish, so i’ve traduced many things)
Explanation of halo 4 720p(its on spanish)
> "Resolutions of the Halo saga this generation have always been somewhat controversial. Really very few games work exceeding 720p natively on PS3 and Xbox 360 (and if I apuráis, I at least know of none), but is that Halo started on the wrong foot in this generation are the "Sub-HD “shown in Halo 3. ¿Halo 4 will run the same fate?
>
> Halo 3 and ODST native moved to 640P (rescaled to 720p) resolution below the mean, some people described as sub-HD in their day.
> Hence those pesky jagged lines that your eyes seen, they were grunts with big blocky jagged lines.
> With the release of Halo Reach keeps getting better remarkably, Bungie is pressed while the belt and climbed to 720p native technique using a custom anti-aliasing to smooth edges that left a very refined technical section.
>
> What has been the thing end?. Development director Frank O’Connor has responded by reassuring the fan community since Halo 4 would run in 720p native with a motor, rewritten from scratch, it had nothing to do with Halo used in CEA.
>
> This is good news because it probably will look better than Reach but have not said anything about the system they will use anti-aliasing, so each judge, while not having a resolution similar to Halo 3, me and me is fine.”
So 343i are doing the things right, and pushing X360 to his limits!