Something can totally suck as an adaptation, like the new BSG or the Bixby/Ferigno/Johnson Incredible Hulk, but still be a good show/movie/whatever in their own right.
I just don't accept the premise that what makes something work as an adaptation is its accuracy. "Adapt" literally means to change to serve a new context or purpose. So whether something succeeds as an act of adaptation depends on what purpose the thing is being adapted to serve. Often, the purpose is to change it in a way that will make it attractive to people who weren't fans of the original. So I'd say both your examples succeeded as that kind of adaptation -- the kind meant to take something that was regarded as silly and frivolous (or, in the case of BSG, something that fell far short of its potential) and reinvent it as something more sophisticated, something that would appeal to audiences who had no interest in its original form.