Most of the people I've dated in my life are basically good and even marriage material-- but they weren't for me.
How did I know? Well, after being in a really horrible relationship for nearly three years (this was, unfortunately, my biggest learning experience and this guy did not fall under the 'good for someone else' category at the time I was dating him, at least), I had a pretty good idea of what was bad dating material, what was really important, and what things I could be flexible about.
Most importantly, the guy had to be interested in marraige from the start. I'm not talkign about 'oh, maybe in three or four years' or 'I see marraige in my future' or 'when I get a better job and an income.' No. I mean someone who believed that they would be better off married at that time and who just hadn't yet found the right person.
Also non-negotiable was that I had to be comfortable with him and him with me. This seems obvious but it's actually a lot more common than you think for people to be uncomfortable with their partners. Being comfortable with someone means not having to think twice about calling them on the phone. I'm talking about the dating stage here. Obviously, if you know that your significant other is in an important business meeting or in trying to focus on writing an exam, you're not going to pick up the phone. What I mean is (c'mon, you've all been there) is 'what will he think of me if I call.' Then there's the waiting by the phone for a response. No. Nada. A guy I met on the plane (actually I was spelling out my woes to him about that no-good relationship I was describing above) said to me "we only want to be with people who want to be with us too." Simple yet profound, and really not taken seriously enough in choosing a spouse or a partner.
Next, the guy had to be dependable. My husband is what I call a time optomist. He always thinks he has more of it. This leads to being late and a lot of rushing around. Still, he's what I consider dependable. When we were dating, he had reached a crossroads and had to decide on what to do next with regards to occupation. So on the surface this seems like a non-dependable thing, but what I saw was that he was taking active steps towards founding a carreer for himself. He'd also been working ever since high school, so I knew he was no schlepper. It wasn't particularly important to me what profession he chose, as long as he was able to contribute his share to the life we wished to live together. It's nice to have big dreams, but you also have to work towards achieving them. This is not petty thinking. Love and romance are all fine and dandy, but you can't eat them and they're certainly not enough to finance an annual vacation abroad. Love and romance alone won't even finance a tent at a campsite.
On that note, he also had to be dependable emotionally-- contribute psychologically to the kind of lifestyle we wish to live. Family first, that kind of thing.
There were other things I learned to look for along the way like the guy's relationship with his family and if I could handle his moods. We all have moods, but not everyone can respect the way other people experience them. I was dating a really nice guy for a while who was really the perfect boyfriend. He wrote poems, brought me really thoughtful gifts, made me dinner-- everything. He also had a good job future ahead of him and had a great relationship with his family. But I had to break up with him when I realized that I just wasn't able to be nice to him in the way he needed. He would get anxious in ways that really bugged me. I wasn't abe to cope with these episodes, as minor and brief as they were.
Mutual respect is also incredibly important. It's not necessary for someone to be at the top of their profession or the most, best, finest of anythign in particular for you to think well of them. You should also feel that the other person thinks well of you.
If any of these conditions were not met, I wouldn't even have dated someone. Two or three meetings are enough to establish these facts wihout falling in love. Why waste the time and energy of love and a relationship on someone you're eventually going to break up with?