Between man and women--I don't think love should be unconditional. No way! My love comes with conditions. I think I might be considered emotionally high maintenance.
Between parent and child, unconditional love is that thing that blinds us. It is biological, I think.
For pets! Unconditional, and the way they love us is also unconditional.
Again,with reference to men and women ( or same sex romantic partners)--there are some people who love unconditionally. I am not one of them. I expect certain behaviors in return for my love, behaviors such as respect and courtesy.