forgable firefight/campaign
bigger maps
more options/all playlist and game modes
more custimizations
more people allowed in theater(party leader controls the video)
a higher max amount of players allowed in a playlist
a multiplayer that kept us playing like halo 3
a different ranking system that depends more on the skill of a player than how much he played
Ai integrated in some gametypes(infection,invasion)
and a great campaign
more drivable vehicles
more species
IT IS NOT COMPLICATED