Sorry if I cannot tell if you are being sarcastic or not.
The Sangheili play at least 40% of the Halo Storyline, Spartans being 45%, and the Covenant 15%. The Arbiter played a big part in both Halo Two and Three; and was not included in Halo Reach knowing that it took place prior to the events of Halo One.
Halo isn't just about aliens, you are right; the UNSC and ONI still have to deal with rebels.
Loadouts = COD, 'nuff said.