Would definitely say that the frame is the main part of the bike and most other parts are consumables or will need replaced after enough use or misuse.
Foe example, lets say you had two bikes bought new and with all original parts still intact... a Trek and a Bianchi. You moved all the components from one, onto the other and vice versa. You would surely still identify each bike by the frame... the Trek is still the Trek even with all but 1 part from the other bike.