Despite claims that not all original Xbox titles will run on the next generation console, the Xbox 360's backward compatibility and graphical enhancements for the first two Halo games have been confirmed by Bungie.

To mark the one-year anniversary of Halo 2 on November 9th, Bungie released an update on its website, confirming that both the original Halo and Halo 2 will be compatible with the new console, including Xbox Live play for Halo 2.
Bungie claims that they didn't redo any of the old textures or geometry, but owners of HDTVs will see something special, since the games are running at a higher resolution.