The Batman 66/Batman & Robin popularity thing comes down to the times.
I think it was a matter tone. Batman & Robin had two preceding movies that had a dark gothic tone. Batman Forever wasn't as dark, but was okay. Going from the Tim Burton movies to the day-glo abomination of Batman & Robin, in effort to sell more toys was the biggest mistake (that everyone involved with has apologised for on numerous occasions).
Saying that though, as dark and gritty as Batman currently is, I LOVED Return of the Caped Crusaders. Funny as all hell.