Reading this thread reminds me of some of the time I spent on an unsuccessful D&D thread. I'm of the opinion now that designing characters for a genre is much easier if you're a fan of it. I tried some Tolkien material, to put the short end to it, and got some pretty wild feedback (some of it positive) but in the end it all confused me and I got frustrated and gave up on the idea.
I know you don't have to be a fan of a genre to write it well (look at what the EGB series writers accomplished, they weren't GB fans), but it helps. But you do have to be motivated to write successfully.
I know what it's like to feel unsure of yourself, but that's where the discipline to learn as much as you can comes in. Just study the genres, talk to people about your writing, and make your decisions based on how these things help you. Good luck!