I was gonna say.
The only reason people stopped playing Halo 2 on Xbox Live is because Microsoft took the servers down. Halo isn’t as popular as CoD, sure, but it’s still always going to be one of the top sellers for whatever iteration of the Xbox is current.
On topic: I prefer the style of Battlefield over Call of Duty. BF is built to promote teamwork, CoD is built to promote running around with one of the three imbalanced guns that outclass all the others and do as good as you can alone. I’m not the greatest player when it comes to FPS games, but I can get behind helping out my team a lot easier than I can get a 25 kill streak with the UMP to call in my nuke.