Black ops 2 lag

Your best connection would be an ethernet cable and that way you eliminate any chance of wireless interference with another device. Have you downloaded the new Nvidia Beta drivers that optimize your video card for Black Opps 2 (310.54).
There is also the possability that your getting lag from your ISP which would be beyond your control.

Would a usb to ethernet adapter work as well as a standard ethernet mport on a mobo? my ethernet port does not work  

There are two ways to do this and one is the usb to ethernet adaptor and the other is a network card that fits in a x1 slot, The first link is to a usb 3.0 connection which would be better than a usb 2.0 and the second is to an Intel x1 slot card and Intel is the better choice in ethernet cards and you can get cheaper ones.

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Thanks, i just tried campaign and it was laggy too   maybe it is my pc aswell?

http://www.dslreports.com/tools

This web site has some good tools for testing out your computer and internet connection and you can optimize things a bit by changing some settings.
Have you wired your router to the Pc yet ?

Another thing you can try is to play around with the game settings . you have a good looking computer but in looking at the components the weak link I see is the video card. When gaming the single most important part is the video card so to see what is atually causing your problems try adjusting down some settings starting with AA and MSAA and the ambient occlusion. I know a lot of people likt o be able to play a game maxxed out but to do that you have to have the equipment to do so and while maybe you have always maxed out all your games this is brand new and maybe it's getting to the point where the video card can't max it out and you need to tone down the settings.
Naturally this is just a suggestion to try and see what can be causing your lag and it may not be the video card at all but you need to find out if it is.