Don't just think about what's popular in general, think about what you want to do as a dev, and what you're good at doing. From your post, I don't think your written English is good enough yet to make a dialogue based game (but, of course, you can always get a writer from the Help Wanted forum). Trends change constantly but if you make quality games that would appeal to you if you were a player, they will appeal to other people too, and you can build your own niche from there :)