DoD 3, haven't played 4 yet. I don't have an xbox myself, but regardless I'm not unfamiliar with how to kick ass when I play at my friends house.
Halo 3 definately is able to make its self look fancy, but the combat is pretty crappy in my opinion. But what can you expect when you're shooting at talking aliens with a pink laser cannon that sounds like a Nerf gun when fired.