Setting aside the questions of whether Batman should be serious, just looking at the 1966 Batman
as a television sitcom, it was, quite simply, a good sitcom
. It was clever and funny, with lots of smart humor and imaginative situations. It had a terrific cast of mostly top-notch actors (Burt Ward notwithstanding). It had excellent production values and set design. It was one of the most innovative sitcoms of the era, with its own distinctive style and approach unlike anything else on the air. And it tapped into the zeitgeist of the era with its mod designs and psychedelic colors and wry, subversive send-ups. For a couple of years, it was a huge pop-culture phenomenon, getting all sorts of press, inspiring nightclubs, etc.
Of course, it wasn't all good. The writing started to decline some in the second season, and was downright lousy in season 3, whose one bright spot was the introduction of Batgirl/Barbara Gordon. But at its peak in the first season, it was a really fun, well-made, worthwhile show, and the same goes for the '66 feature film.