Game making isn't that easy, hence it costs a lot of money and effort to make games like Halo, Gears of Wat etc.
There are game makers that are good that require no programming knowledge - but to get something as good as those, you'd need to be a pro at what you do.
If you are willing to program, Dark Basic Pro is a good start, it's worthy picking up and learning. If not, well FPSC X10 is out soon, which also can be bought off of this website which allows you to make FPS games with Direct X 10 graphics (This of course Requires Windows Vista, a Direct X 10 graphics card and Direct X 10)
Making your media - that being your characters...well you'd need to learn 3D modelling because I doubt people will do it for you unless 1. You pay or 2. They're generous and you have a good project with good progress on your hands.
Making games isn't an easy-to-do process and takes some learning. There really isn't any 'story makers' the make games like Gears of War, (The companies create their game engine in C++ and use that to build their games, but they tend not to give away their games engines for small price, in fact they're expensive and some of them are actually harder to learn than Dark Basic Pro)
Your best best is if you have Vista + Direct X 10 graphics card - Play with FPSC X10 with their free media and model packs...
Or if you don't FPSC
If you want to learn to program, grab Dark Basic Pro.
Making the media, well depends on what kind of learning curve you want and how much you're willing to spend.
I love Nancy DrewG, but not insert brain here