If they were serious about living happy, healthy lives, they would be working to improve their situation. Either by working on their relationships or moving on to find whatever is missing in their lives.
If any of the men you are interested in isn't willing to leave his wife prior to beginning a relationship with you, I would take that as proof that they aren't looking to improve the quality of their lives, and that they value the relationship they currently have more that any potential future with you.
If any of the men you are interested in isn't willing to leave his wife prior to beginning a relationship with you, I would take that as proof that they aren't looking to improve the quality of their lives, and that they value the relationship they currently have more that any potential future with you.