cod 1, uo, 2, 4/mw, mw2 and blops1 are all pretty good. haven't even played the majority of the halos.
I see a lot of people would rather play with barbie. Which pretty much confirms my theory.
never played either
If I had to choose, Halo because it's a sci-fi setting. Cod is just a bunch of dudes with small units yelling at me to do things quickly.
Lol small units.