It was always a toss up between Anders and Fenris.
Anders would originally steal my Hawke's heart, especially when he would show off the Anders that I fell in love with in DAA. The sarcastic, charming and deep down hopeless romantic. But as the game goes on, his beating of the "freedom to all mages" dead horse and depression (that would eventually lead into homocidal tendancies) would eventually kill any kind romantic feelings I had to be replaced with the urge to punch him in the mouth.
Fenris had a darker outlook on life that for some reason always appealed to me. His smoky, broody nature with his voice was enough to make me melt. Over time he shows his romantic and softer side. His personality was always a nice fit with my humorous Hawkes
In the end, I think Fenris wins out.