The notion of gentlemanly conduct has taken quite a beating in the past few decades, not least from men themselves. The idea is very simple, really. It involves men taking a slightly extra strong turn at treating others the way we'd like to be treated ourselves. Carrie Lukas has a nice article on the subject on National Review Online today.
Pointing out that men today are less likely than in the past to give up a seat on the bus for a woman, much less a spot in a lifeboat as the men on the sinking Titanic did, Lukas notes that the ideal of the gentleman is not about how they treat women but how they treat people (and animals, and inanimate objects, and indeed everything) in general. A true gentleman respects other people and the creation that surrounds him, and he does so because he recognizes and accepts his place in the world:
Gentlemanly conduct isn't about women at all. It's about men and their sense of themselves.
Conclusion: Western men don't expect as much of themselves as they used to, and that's exactly what we get.