I tend to prefer romances where the characters aren't stunningly attractive in a generic sense, where there are definite imperfections, even, but there's something that grows on one another with time. Sometimes it's a matter of a personal quirk--a way of smiling, or some other mannerism, that calls attention to a feature or personality trait that is compatible.
I tend to go for heroes (and heroines) who are dark of hair and eye, maybe because I am, and I hated the way people with brown hair and brown eyes (the most common combination in most parts of the world) are so underrepresented in fiction. But any hair/eye combo can be attractive. Hazel eyes are also underrepresented. Heroes tend to have eyes of blue, green or steely gray. Hazel is a pretty common eye color (if you look, most people with "blue," "green," or "gray" eyes really have hazel eyes) in European settings, but it's infinitely variable. And it's rarely represented in fiction.
Hair and eye color are only one part of a person's appearance, though, and sometimes I think writers bank too heavily on those traits instead of the thousands of other ways two people of the same coloring can differ.