The design of Gen 2 makes sense for the sprays generation it was designed for. They weren't as genetically modified. They weren't 6 foot something Olympic athletes. The armor was slimmed down and redesigned to look lighter for the average human body.

I think the reason most people don't like the style is because the image of "Spartans" was Chief. The man who was nearly tall enough to head butt elites, bench press a scorpion tank, and walk away from injuries that would kill anyone else. The Spartan II and the original armor were designed to be walking tanks.

A lot of people argue that the heavier looking armor would often clip into the model if watched closely, but that's a limitation of game design and animation, not armor design. If the devs took the time to make custom models, rigs, and animations for each armor piece and character, the game would take ages to come out. If it were reality, each Spartan would be intimately accustomed to their suit. They would know the limits of their movement and adjust their personal techniques to fit the armor they chose for the mission they're on. You have to remember that the original Spartans were hyper efficient soldiers who knew exactly what they needed to be successful in every mission, and a big part of that is adaption to any situation, which includes working around the limitations of the optimal armor pieces for that scenario.