My list... (not that it matters)
-Online 4 player co-op
-Co-op campaign w/ online
-The ability to jump into co-op or online at any time like in warhawk
-More color (Less photo realistic and more CG like)
-Better character models(chimera and human)
-Replay/movie save feature
-Weapons are good just improve them
-Add shield and/or cover system
-Offline sprint
-Custom Soundtrack
-More vehicles air, land, and water
-Take out the intelligence documents and make them part of the story(most people don't even know who the cloven are or who their leader is)
-option to switch to 3rd person
-Better fire(flame thrower/ fire incendiary grenades)
-Destructible environments ala killzone 2
-Water physics(when you fall in the water you just fall through in rfom1)
-Knife option
-The ability to pick up stuff and throw it(in case you run out of ammo)..
(you should run out of amo it would make the game more interesting)
-Sixaxis melee attack would be cool
-melee grenade attack(stick a grenade inside chimera's mouth and watch it blow up)
-Shorter Title
-When you step in snow/sand you leave foot prints
-This last one would be cool but I would understand if they don't do it. If you get shot the holes appear on the clothing. If you get burned the clothes get singed. If you get wet your character looks wet.(speaking of getting wet how about water grenades? they would look bad ass) Also blood would be cool w/ the option to turn off for kids.