It could be that the characters are not developed well, making it hard to connect with them emotionally. Also, the story might have weak conflicts and resolutions.
It could be a very strange or ungrammatical way of expressing something negative about a love story. Maybe it implies that the love story is not good, like it 'sucks' in the sense of being bad or unappealing.
Well, here's a suck love story. A girl fell in love with a guy who was already in a relationship. She knew it was wrong but couldn't help her feelings. She tried to get closer to him by being friends first. But as time passed, she found out that he was just using her for emotional support while staying with his other partner. It was a really sucky situation for her as she got her heart broken in the end.
Another way to look at it is that it might be a misphrasing of something else. Maybe it was supposed to be 'you suck at love stories' which would mean that you are not good at dealing with, understanding, or creating love stories. But as it is, 'you suck a love story' could be a very unique, individual - specific expression that only the person who said it really knows what they meant. It could be based on a personal inside joke or a very specific context within a group of friends or a community.
One common element is miscommunication. Just like in a lot of relationships that turn out bad. People don't talk clearly or they assume things. Another is unrealistic expectations. For example, one person might expect the other to change completely. And also, dishonesty can play a part. If someone lies about their feelings or what they've been doing, it can make the love story suck.
One type could be intense plot twists. When a story takes an unexpected turn, it grabs your attention and makes you eager to know more. For example, in a mystery novel where the prime suspect turns out to be a red herring and the real culprit is someone completely unexpected.
I'm not sure what exactly you mean by 'wife and i suck story'. If you mean a story about a difficult or challenging time with your wife, here is one. Once, my wife and I planned a big vacation but we suck at packing. We forgot so many important things like our toothbrushes and chargers. It made the start of our trip a bit chaotic.