Batman share more than enough of the commonalities of the fictional characters classified as "superheroes" to claim the pedigree. He wears a costume and keeps his real identity a secret; he has a hidden headquarters; he uses special equipment, ranging from miniaturized devices he keeps in his utility belt to vehicles like the batmobile and the batplane; he has the legal status of a deputy; he associates with other so-called superheroes and is a founding member of the Justice League of America, a team of "superheroes"; he often fights individuals who qualify as super-criminals; he defends common people and will risk his life to protect the common man; he can be summoned by the police through the use of a special signaling device (the "bat signal"); he has special skills which he uses to fight crime, ranging from a mastery of certain fighting skills, to the use of disguises, to the mastery of certain forensic sciences, to a unique understanding of psychology of the criminal mind, and he is a very good detective. Batman also answers to a higher moral code than does the average man.
Interestingly, the term "superhero" has been traced back to its first appearance in a 1942 story by Joe Simon and Jack Kirby, when it was used to describe the costumed character "the Guardian," who also had no "super-powers." The term "super" is a coinage of the 1920s, when iit came into vogue as a contraction of the word "superior" and should not be construed as always meaning something beyond the ability of ordinary humans; "super" does not have to be synomymous with "impossible." Note that in the link below, it is clearly stated that "characters need not have actual superhuman powers to be deemed superheroes." Batman is also served up there as an example of one of the world's best known "superheroes," and he is the prototype of scores of costumed heroes who have no superhuman powers. Clearly, Batman qualifies as a "superhero" and opinions to the contrary are exactly that, mere opinions, and may be ignored with a clear conscience.