Superiority is the quality of being better than or superior to someone else. Your superiority in the sack race won you a first-place ribbon.
Superiority refers to the best. It’s better than, above, greater than everything else, whether there’s something to compare it to — the superiority of one ice cream flavor over another — or whether it just describes a general state of high quality — the superiority of the University library. Of course, sometimes superiority is all in your head; in that case, some people might say you have a superiority complex, which means that you think you’re better than everyone else!