Bob Kane, actually, was very much the creator of Batman. Later contributions, as happens in all comics, were from Bill Finger, and eventually by many others. There are several co-creators that could be assigned to any comic book character, particularly one as developed as Batman. Bill Finger was an eminently talented comic talent, but he wasn't the true creator of Batman. All comic characters eventually have other contributing creators in this sense, quite often in the original years, but the character of Batman was definitely the creation of Bob Kane. Bob Kane and Bill Finger, as with so many other great and legendary teams in comics, made explosive and exemplary team-up contributions to comics.
