I have a hard time comparing Halo and CoD, even. Halo is an unrealistic, over the top, sci-fi shooter where the protagonist has buckets of health and the jumping boots of Ra.
Call of Duty is a modern-based realistic gritty approach to the FPS. Both fillout their niche's correctly, and it's all quite smooth in the industry.
already so many topics been made in the past about cod vs halo n blahhhh...but for me i will always choose cod over halo...infact i will choose anygame over halo sense that game is overhyped and full of little kids screaming