There are six qualities I expect in a relationship with a mate.
1. Honesty 2. Trust 3. Loyalty 4. Love & Devotion 5. Intimacy 6. Emotional security ( which comes from knowing I can count on them through my ups and downs).
I've always been fascinated as to why we say "yes" to one person and "no" to another. Where are with regard to the phases in our life and our maturity is a major factor. The type of person you wanted in your life at age 16-19 is likely different from the type of person one would want at age 35-45 and beyond.
We're constantly evolving and learning more about ourselves. In the end it comes down to two people who grow together overtime as opposed to growing apart.
Having said that there is always some minimum requirements before one would even consider going out with an individual. Naturally for me I have to be (physically attracted), identify a (nice personality), share a similar (sense of humor), and be made aware of a feeling that the (attraction is mutual) via flirtatious banter.