Ah, if I had to make a game on a genre I’ve made before, I’m not sure if I would rank difficulty on it at all. The only difficult part would be to implement something new that I’m unfamiliar with.
For example if I was working on a new platformer, I’d most likely add a new feature, to make it more interesting for me to make.
I prefer 3D games myself, as I think once one gets the basics done, it’s way easier to make a game, than with 2D.