If you could make aiming and AI movement a little more interesting this would be a good game.
Just making a bumpy surface would help. Not just a few bumps here and there, the whole terrain.
Make a recoil effect for the cursor. Whenever you fire, the mouse should move up. It should stay up there, not slide down by itself. Force the player to take recoil into account when firing.
Making small boxes that you can jump over would make taking cover more interesting. The AI should also take cover behind obstacles, especially if the player is near.
I can't give it more than a 3 as it is now. Too much time have been used extra modes and gadgets and too little on physics AI and maps.