I think it was mostly selfish, in that he seemed to view her as an extension of himself. He always showed he had a weakness for anyone who would claim to love him and value him. However, I think one of the least selfish acts in his entire life was taking her to Cardassia with him and openly claiming her as his daughter. He lost a great deal in that act, but he refused to renounce her. Like most things with Dukat, there's no easy black and white answer but a confusing blend of gray.