The Adama/Baltar dynamic was as essential to the show's appeal, in my opinion. Certainly the contrast between the two helped to keep the issues of the series in focus.
And both actors are dead.
It doesn't sound as extreme to a British fan - everyone has their favorite "Doctor", everyone their favourite "Bond". We may criticise other portrayals, but we don't deny their validity.
I feel that you do the current generation of actors a slight disservice here. Because we grew up with tnem they may be Starbuck and Apollo to us, but that doesn't neccessarily mean other performers wouldn't be any good in the roles. Rather, they might deepen the characters by accentuating different aspects.