This is how I feel, Halo should stray away from the realistic graphics while still remaining grounded to reality.
The best examples of this are are not in any one game but across several. Halo 1-2 have very Cartoony looking concepts and graphics that go hand in hand with the cyberpunk settings, positives of this were limiting Enemies to the exact same skin with different color and making them fo-reflective chrome so they were easy to register as “hey that’s an elite/grunt/MP spartan”. Simplicity is key and the time to register what’s on screen and reacting to it is the name of the game in an FPS. Juicy, rich colors can be seen almost exclusively in the first two games.
A bad example is Halo Reach which plays well but the difference in all the Elites plus the boring pastel colors and over saturated textures and hyper detailed models make it hard for some people to register an enemy from long and sometimes medium distance.
Some of the best “realism” are the things people don’t like talking about (which are also my favorite things) like the evenly spaced out and functional design of the Gen 2 armor, which takes the concept of Reach’s Spartan armor placement and makes it beleiveable with its maneuverability but high fantasy in its shapes of the armor. Another is the Halo Reach Sniper Rifle which has such amazing shapes to it compared to the snipers we have seen but in real life would be absurd and unwieldy.
Bad and examples include things like Master chief in Halo 2-3 only because his hip/crotch/thighs/shoulders/back torso all clip through each other, meaning they in real life would limit range of movement to less than that of what we see in the games, thus breaking the suspension of disbelief for many who say old mark 6 is more realistic then gen 2 mark 6. There is an amazing image of halo 3 chief T posing, and the way they get the model to do that without the shoulder clipping the torso is by pulling the arm and stretching it, based on that if chief needed to move the way the books or even the game implies with the old suit he would rip John’s arms from the socket or worse. (It should Be known full MOCAP didn’t exist in games until reach, this was the best guess they’d had at proportions) (EDIT: Bungie also admitted after halo 3 was made and reach began production that they screwed up proportion on how the armor should be designed in both vidoc and live play)
another example of bad “realism” is the halo Reach and Halo 4/5 marine uniform which is bulky and busy compared to the sleek yet unrealistic Halo 1-2 designs which are just standard green/grey uniforms with armor plating and rubber tread (like the marines from aliens) which are by no means credible protection but look more flashy and visually appealing to the viewer.
There are a lot of hit or miss when it comes to realism and halo, I firmly believe that’s because Halo started and was meant to stay “unrealisitc” by traditional standards, instead it takes something not realistic in shape and form and grounds it in reality by how it’s seen in motion and interacted. This is why brightly colored aliens with spikey chrome armor and 7 foot tall green cyborg mech suits work when reality says “that’s bogus”.
Life, REALITY in general has a lot of dull colors and overflowing detail. Your Eye and mind don’t process it all and tend to simplify details. I Have a 4 year degree in Illustration and Design, one of my favorite teachers said “reality is visually boring, the mind in memory tends to enhance colors/features based on how we perceive things and not as they are so they are more exciting to us.” And the More you study the subject the More you understand something streamlined is more often then not easier for the viewer to digest, and that “more details, more gritty colors, over saturated multiple texture layers” aren’t real answer.
One last thing: I really like the halo CE/2 models for chief because he has worn battle elements like damage/scuffs in his armor but it still reflects a polished high green series of colors when you see it move which was abcent in every game after except halo 5 (but only really close up) and that feels like the best compromise realism in a high fructose fantasy universe like Halo.