It can be healthy and normal to compare yourself to other musicians, especially if that is your profession. You see someone who plays something you like and you try and analyse what it is you like about their playing, and maybe what your playing lacks. It can motivate and inspire you to become a better musician.
It becomes unhealthy when you can't be happy just because someone is better than you. If you have something to offer as a musician and can move an audience, who cares if someone can play louder, faster, more complicated pieces. Music isn't a sport, there are no champions. Even a competion winner is only the "best" in the eyes of those particular judges in that particular performance.
None of what I am saying says you can just be lazy and shouldn't devote yourself to being better, but I also don't think that everyone who isn't the "best" should just quit music. You have to be realistic if you are going to try to be a professional musician however, if you really aren't as good as at least some of the people that you will be competing for work with, then you may have to rethink how you will make your love for music turn into something you can make a living at.
Most successful musicians aren't the best technical ones, there is the "X" factor, how do you entertain or move and audience. If you are comparing yourself to pianists that are in that small niche of music that only think in terms of technical genius, then of course your options are limited, only in that world are the best musicians considered successes. In the overall music world, they aren't even considered as worthy of note, most people just ignore that whole scene.