I'm a guy and consider myself to be bisexual. I would rather be totally heterosexual, but since my wife has no interest in sex, I need to find relief and enjoyment somewhere.
I have no interest in men romantically and don't like any huggy, kissy, or anal activities. My common denominator seems to be that I like cum, whether from a well-fucked pussy or from a hard cock. I enjoy on the wetness of it all.
I think that the essence of being bisexual is just liking the genitals of both sexes, without the romance, although I know that some might disagree with me on that.