Fun fact: 9/10 users with no linked gamertag are better than you at Halo. That doesn't necessarily mean that I am; but it does mean there's a pretty solid chance.
I'd give you a 4 out of 10.
Don't have much to go on considering the only vaguely competitive 'lists on this game are Arena and MLG, and you haven't played a great deal of either.
Your K/Ds are distinctly average, and you've played nearly 2500 games of BTB. Lots of Living Dead and Grifball screams wonders about your play style, and the fact that you're only vaguely positive in both isn't exactly encouraging.
That said, you're positive with 3 out of 4 precision weapons and have a (very slightly) above average win/loss.
You're below average, but there are worse players out there.
[Edited on 11.03.2011 7:30 AM PDT]