A lot of people say that having things in common helps the longevity of a relationship. For me personally, I think communication is one of the most important things in generating a good relationship. Besides from that trust, and how comfortable you around them are also factors I'd consider as being the most important.
I came in here thinking every gurl would be writting money as one of
but waiT
I find it awkward when a guy spends too much money on their boyfriend/girlfriend...it's like they can't be please them in other ways. Personally I prefer a guy who knows how to spend money on himself and dresses nicely.
Trust is a major one, an insecure partner is sure to lead the relationship to failure. Respect for your partner's differences is also important, if you're constantly trashing on your bf/gf for something they believe in or something they enjoy that's not gonna work. Support for your partner when they need it, if they can't turn to you when things are rough then they'll just turn to somebody else.
Why on EARTH was this given a warning
It's literally this basically, although just a good and compatible sex life is probs a better replacement for the good dick.
I'm not saying that it's in the three most important things, because that's debatable but sex is quite important in a relationship. And I'm serious, it really is very important.