http://www.ign.com/articles/2014/10/07/the-horse-you-rode-in-on-a-halo-the-master-chief-collection-story-ign-first
Sounds better than the early previews.
Quote
For those of you who like to start message board wars over such things, let's get this out of the way: Halo 2's campaign isn't quiiiiiiite 1080p. Due to running the original graphics engine and the Xbox One-ified Anniversary graphics engine simultaneously and the original Halo 2 audio engine and remastered Anniversary audio engine simultaneously, Halo 2's campaign does run at 60fps but, resolution-wise, clocks in at 1328x1080. Here's an explanation from 343 executive producer Dan Ayoub: "During development we were really pleased with the way the engine and buffer allowed us to switch instantly between classic and Anniversary engines that are running simultaneously - however that, as you might expect, put a hit on resolution. The campaign of Halo 2: Anniversary looked fantastic at 720p with the level of detail and clarity it gave us, but like every other aspect of the game and tech, we wanted to push it further. So in the last weeks of development, our teams were able to meet a stretch goal and the campaign of Halo 2: Anniversary now runs 60 fps at a crisp resolution of 1328x1080, which is a significant and meaningful boost in image quality we think fans are really going to appreciate. All of the other games across the entire package of The Master Chief Collection run 60 fps at 1920x1080 native."
Sounds better than the early previews.