I always find this topic to be really interesting since there's no objectively correct answer, and it tends to be something people have experience with.

Obviously, the best answer is "let the player pick", but personally, I'm 100% in the inverted camp (both y and x axis, because apparently some maniacs only invert one). I have no idea where I picked up inverted controls, but I've favored them as long as I remember playing games, so I figure some early titles I played had inverted by default, which checks out since I played a lot of vehicle-based games.

For me, one of the worst experiences is realizing a game I really want to play only supports uninverted camera (or in the case of a couple, only supports inverted y), because it totally demolishes my ability to reasonably play the game with any degree of skill.