Resolution isn't everything, nor it is AA, although they both really help. If developers rendered everything at 480p this generation they could try a lot of stunning features and graphics techniques at the same time -oddly enough they are achieving this in games like Crysis 2 and Battlefield 3 running at 720p, or very close to-.
Nothing beats crisp graphics and nice environments with a good art style!
i.e. according to the numbers, cold numbers.., Halo Reach is sub-HD because the HD standard is set at 1280x720p, while the game runs innerly at 1152x720p.
Yet developers managed to make the game look very crisp -you can see how vibrant the graphics are when looking at the ship's wing-
http://www.youtube.com/watch?v=q7E1XvZR3Nw&t=1m45s&hd=1
Compared to a full-fledged 720p game like Fable 3, Halo Reach looks a lot more vivid and sharp than Fable 3, for instance (at least to me anyways, while Fable 3 looks dull and rather faint in comparison). And the same can be said about God of War 3 being so crisp compared to Killzone 2.
Hope you have a good week! :smile2: