There are so many things that can be done under graphics design. It's not possible for one person to cover everything in the field. This is why graphics designer always choose an area of focus to base their job.
Some of the fields in graphics designing are 3D Designer, Video game designer, Visual designer, Creative manager, Art director and Concept artist etc.
Which one of those fields in graphic design pays the best?
I wouldn't say that there is a particular field in graphics design that should be considered the best other than the one that you have perfected the learning so well that you can consider yourself a professional to deliver a high quality job when you are being hired to do so.
None of the above you mentioned is the best. All of them are serving their purposes. Just find your niche, learn and become a professional, then use it to make money as much as you want.
The best field in graphic designing is the field where you have the utmost skill to deliver on so that should be where your center focus is. If you don't know how to work on a particular field, you can never consider that area to be the best.
The best is subjective. Even a graphic designer with knowledge on all those areas will definitely have one is more interested in. And that, to him is the best.
Creating of animation is a fielding graphic design that I excel in very well. I can categorically say that it is one of the best section in graphic design profession that I enjoy.
