I really hate it when people try to compare FPS titles and mention skill gaps and randomness. Neither is a legit claim. Skill is purely perspective and independent of each title. The skill sets of Halo games vary across them all. Same goes with CoD and Crysis, each game holds a different varying set of base skills one must possess to be good at each one.
Randomness is based on equations, not magical random events that just happen for no reason. Lag plays a huge part in this, but is so often overlooked that it becomes easier to blame the game mechanics. All FPS, suffer from some sort of either lead time, magnetism or bullet spread that works differently in all titles. Just because it's there and it sometimes fails to work to your advantage, does not make it flawed or poor.
That being said, going backwards in gameplay will only delay and separate gamers. Halo 3 and 2 were great games, but bringing back that same gameplay, would take the franchise back a bit, and disrupt or destroy any future plans or innovations that the franchise may have planned. Why do you think they ultimately decided not to include CEA with it's original MM experience? They stated directly that doing so would have fragmented the player base. Fragmenting it by destroying other titles the chance to be played because of the unique experience the original had.
Seriously...it's been 2 titles now, and you guys are still bitching and moaning about the changes being made to the franchise. 2 games and six years.....they obviously are going forward with innovation. Except it and move on, or leave the game. That's pretty much your only choice.