Definitely Halo.....way better story, graphics, and guns. COD i think has a larger fanbase but idk why. They buy the same game every year. The graphics havent changed in 4 games. I could go on forever about this.
Black Ops 2, gameplay is amazing, they've established themselves as argubly the greatest game franshise ever and Black Ops 2 shows it, Great graphics, gameplay and quality. Not to mention a pretty dang good story. COD hands down