Well, let's see... of the top of my head:
- Dedicated servers
- Destructible environments
- Ballistics, instead of absurd (for a realistic looking game) "hitscan" lasers.
- A real class system, with all the balancing benefits of one, as opposed to the "faux" and horribly implemented system CoD has.
- Interesting maps
- Some vehicles would be good
- The removal of idiotic and overpowered killstreak rewards (namely... all of them)
- Rework of the perks to actually be balanced
- A more streamlined unlock system... Nobody wants to grind for 50 fucking years to be able to play the whole fucking game they paid for...
- Actual customer support
- A reasonable price
- A better graphics engine. Maybe one that's updated and not based on an engine from nineteen-ninety-fucking-nine
- For players to not be made of waffles so weapons with different damages actual matter.
- Weapons that behave differently, to a level where it matters, and don't just come in different skins with negligible differences
- Some semblance of balance
- Removal of retarded additions like akimbo, thrown knives and riot shields.
- Amazing and extremely immersive sound.
In general, make the multiplayer excellent and enjoyable unlike the giant bag of suck it is now.
...OH WAIT: