Hi sadeshmagic, thanks for responding. That was exactly what I did. I copied the whole Whatsapp folder (including sub-folders) and pasted onto the device storage. During setup, Whatsapp did recognise that there is an existing database and prompted if I wish to restore it, which I did. However, 2 seconds after restore is completed, Whatsapp stopped working. When I access Whatsapp, there are no old chats.
Tried going back to my S2 and making backups again then copy the Whatsapp folder to the S4, but the same thing keeps happening.