I'm going to be brutally honest with you.
You're not going to get anybody to join. Not at this point.
Why? First of all, there are already tons of Gears of War and Halo fan forums out there, much bigger ones too. Tell me, who would want to join a brand new inactive Gears of War forum when they can just go
here or
here or
here and talk about it there? Who would want to join a brand new inactive Halo forum when they can just go
here or
here and talk about there?
Secondly, you do realize that these are games that have been out for a couple of years and likely already have hundreds of other established communities & fansites, right?
Thirdly, you're advertising completely wrong. You're not supposed to go an active an empty forum with TONS and TONS of empty boards. That will never work. You also have way too many categories and boards. Cut them down by a ton.
Don't take this post as anything personal or offensive, it's just advice.