Let me make this clear, I'm by no means a "Halo hater" and neither am I an anti-mainstream hipster. I've thoroughly enjoyed each Halo game by Bungie, and it's a great series in my opinion. So allow me to say that I was interested in how 343 Industries would handle this series when I've heard they announced Halo 4. They were either going to overhaul the franchise and do something different with it, or they're just beating a dead horse. I was simultaneously worried and excited to see what they had in store for us. But upon witnessing the gameplay footage, my jaw dropped in utter dismay and disappointment.
The campaign footage not only looked exactly identical to prior Halo games, but nothing exciting or awe inducing was to be seen. Besides taking risks with the franchise, it seems they're just catering to the rabid Halo fanatics. Now all the Halo fanboys will dismiss my argument and say "b-b-b-b-but dere r new enemys and wepons!", that's no significant gameplay change. Expansion packs for first-person shooters from the 90s had done that before, and Halo 4 is no expansion pack but a standalone $60 sequel. Halo is now going to suffer from the Call of Duty syndrome, and Microsoft are basically milking every nook and cranny they could get out of this series.
This is rather unfortunate, because the series had great potential. The mindless and tasteless consumer will buy any crap, as long as it has the right name on it. If you complain that the series shouldn't change, then you're part of the problem why the current state of the gaming industry is stagnating and severely lacking it innovation.
EDIT: Allow me to clarify me point even further, I'm not implying Halo is the ONLY popular game franchise that suffers from this trend. However, it does not excuse Halo 4 for rehashing the exact gameplay formula and the gameplay footage was immensely dull.