Trust and honesty are the foundations of a really good relationship but even with trust and honesty you could have a crappy relationship. Even if you throw in good sex, the relationship could be sadly lacking. I believe a couple needs some common ground on which to base communication. As the relationship expands, the common ground does too because they begin sharing experiences but even with good communication the relationship may have problems. Why? Because the one thing that is absolutely imperative, my opinion, to a good relationship is a sense of humor. You have to be able to laugh together. Laugh at yourselves, at situations that are truly absurd, at unexpected events that could knock the wind out of you. You've got to be able to find the humor, together, and laugh. Laughing doesn't mean that everything is lighthearted because most of life isn't but the laughter you share will help lighten the sometimes overwhelming weight that life becomes. So, yes to trust, honesty, and sex but add to that communication and a sense of humor.