Uh huh...the first thing that everyone expect : Multiplayers, with lots of modes, maps, ranks, ... (update regularly) !
+ More weapons (10 weapons for each kind...), abilities, equipments !
+ More zombies, soldiers, robots, aliens kind
+ Add some bosses in campaigns.
+ More achievements.
+ Players can earn some special gifts from achievements (for instance : Kill enthusiast ---> award Frozen Death,...)
+ More specific info about kill bonuses in the profile (the number of kill bonuses, such as how many suprise, Direct hit, Mine your step,... kill do you have ?)
+ More Affects (Natural disasters, Environment Interaction, activating things, blood/gore,...)
+ Better HUD !
+ More gun sounds (they're pretty boring )
+ Add some voices to the characters in campaigns !
+ No maps, modes, weapon types that minus 95-100 % credits !
+ Every objects is destroyable !
+ Harder enemies (the Insane enemies are nothing with me x( ), such as Nightmare, God, Impossible, Severe,...
(More........................................)