2 Answers

A healthy relationship is one where both partners feel safe and secure.  The communication is open and honest.  There is trust and mutual respect.  In a healthy relationship the other person's needs come first... and vise versa.  Love and support are paramount and above all else there is true friendship and joy.

My personal belief is that a really good relationship will have faith at its foundation.  I'm just guessing on the rest of this............
Following that, mutual values and goals, affection and respect.  Both should have a sense of humor and not take themselves too seriously.  The couple will share hobbies and activities, but have personal time as well.  There is trust, and the physical relationship is satisfying!  Communication is pretty remarkable (especially if there is one speaking Martian and the other Venutian).   It's not an "I can't live without you" type of thing.  You CAN live without each other....it's just so very much better with each other.  They are each other's "Wing-man".