What are you creating?
This will always be a valid question. Always. This is because the answer to the question will inform your creative decisions and how you approach a project.
There are all kinds of genres within the medium of comics. The toughest of them to crack, I believe, is superheroes. That’s because there is so much competition out there. Not only do you have to overcome 70 years of publishing from DC and Marvel and the tastes that have formed around those characters and storytelling styles, but you also have to compete with other publishers and self-publishers who are also putting out superheroes. That can be tough.
When you’re talking about horror, the first thing to come to mind will be zombies and vampires (possibly tied for first), with werewolves coming in third. There’s opportunity there, as long as you stay away from zombies. Everything you do there will be compared to Kirkman. There’s also opportunity in the occult. Just think of it differently.
Of course there’s science fiction, which is wide open, as is fantasy. While these spaces may seem crowded, they really aren’t. Not when done well, these genres are easy to do well as well as to do wrong. (Tip: set your internal rules before you start writing, and stick to them. Once you know your rules, you can find your way through the rest. One of the biggest challenges in the recent remake of Friday the 13th was deciding whether or not Jason Vorhees should run. In the first iteration of the films, the character would walk briskly, but he wouldn’t run—yet he would still catch up to or even get ahead of his victims. Deciding if he should run or not informed the rest of what the writers could do with the character and the story. It sounds trivial, but it’s really a big deal. Know your internal rules.)
What are you creating? Answer the question, then go forth and do it.