I am replaying this for first time since launch week.
I can't lie, these graphics rival some what I see on Xbox One.
Halo 4 has a great animation system, high-quality assets and shading for major characters (especially during cutscenes), and a pretty high geometry allocation for non-skybox terrain.
Outside of that, the graphics are alright to meh. Especially when it comes to how the game looks and feels in action.
-Instead of the geometrically-animated water of Halo's 3 and Reach, Halo 4 uses a static surface with purely textured effects.
-Light for light, Halo 4's dynamic lighting is a huge downgrade from Halo's 3 and Reach, and actually manages to fall below the oXbox titles in many ways. Even Halo 1 supports spotlights and configurable specularity, but Halo 4 only supports diffuse point lights. This is presumably why Halo 4 doesn't feature a flashlight, and I suspect the choices behind this compromise are a big part of why Halo 4 was able to reach 720p.
-Some of the methods Halo 4 uses to add "detail" are just plain ugly. Of particular note are the black "shadow" textures which fade away as you approach, which are responsible for some of the smeary-looking areas on Requiem and the general blotchiness of Ragnarok.
-A game as bloom-heavy as Halo 4 is, with as much high-contrast scenery as Halo 4 has, could use better HDR depth.
-Textures on dynamic objects are often pretty bad.
-No motion blur or AO. (Though of course some people might argue that this isn't really a disadvantage relative to its predecessors.)
-This is a bit general, but: aggressive effects work generally sucks in Halo 4. The first time I experienced a large number of plasma grenades going off in Halo 4 was perhaps the flattest moment I've ever experienced while playing Halo. Or, just compare Scarab destruction in Halo 3 to Liche destruction in Halo 4. The former features crazy lighting alteration, huge alpha-blended transparency layers, multiple large physics objects that stick around, and some particles that delightfully smash into the ground; the latter is basically an uninspiring "poof" with a couple of cheap falling objects that quickly vanish.
-Geometric LOD is quite aggressive. Some areas in Halo 4 have a nasty case of clay blob syndrome, and this becomes appalling in split-screen.
-In terms of static lighting, objects transitioning between light levels generally don't look very natural while doing so. Going from sunlight to shadow in Halo 4 often feels like going from sunlight to slightly less bright sunlight.
As a whole, Halo 4 doesn't strike me as significantly more visually impressive than Reach. And I certainly prefer the latter's aesthetic style. :/