in the broadest sense, we receive, give, and share parental love with our guardians from birth and feels for the most part like, if not resembles, unconditional love. in its most beautiful sense, it is a common joy likened to the virtue of friendship where both parent and child derive gratitude in the simple happiness of knowing that the other exists. it usually is loving without perceiving the other as someone to fulfill what oneself lacks, therefore it is not based on suffering/longing that so often influences passion.
romantic love has not been a given presence in our lives and thus seems to stem from our own choice to focus our love on someone we are interested in, though it is probably more complicated than that. perhaps it is a transference love of all the good qualities we've come to understand, then aspire to in a select someone. it begins rather conditionally, unlike parental love (many people have their romantic preferences, yet they love their parents regardless of their own preferences).
also, perhaps you place a high value on the protective quality in the father-daughter love. feeling protected, guided, and supported this way is a very good feeling and reciprocating those qualities in your own way also strengthens the bond. so there actually may be a difference in how you feel between interacting with your dad and other males, just that you're focusing on the same strengths evident in both?