I was really great at Halo CE and pretty good at 2. Halo 3 I was good at off and on it just didn't click well with me. Halo Reach I was fairly good again and 4 I seem to do even better in still but nowhere near where I used to be. I am in my 30s now though so my eyes and reflexes aren't what they used to be and our internet seems to get progressively worse somehow so I'd say age can do it as well as your internet/server's stability. Do you think those might be affecting you?
I don't burn smurfs, I just figured a burning one would smell.