@Ve3tro: "What makes Halo: Combat Evolved Anniversary so special is the fact that it’s not just the original game with some extras.
The team at 343 Industries instead wanted it to be a remarkable re-imagining of the original game. But at the same time it was necessary to also consider fans of the original.
The development team was able to consolidate both by adding the ability to switch between original legacy and modern visuals.
This alone made it worth making this edition of the game a retail release, since the original version can be purchased from Xbox 360 Marketplace. "