Of course the answers depend on one's perspective, and the lack of the ability of one side to see each other's merits is what leads to most of the conflict in the story.
The Igbo culture appears to have a great deal of festive traditions, a powerful emphasis on hospitality and family ties, and they have a powerful narrative of their place in the world and where they fit in. They have a way of dealing with death and difficulty that is very different than the western/christian way the missionaries approach it.
Some of the harder to understand from a western perspective aspects of their culture might be things like leaving baby twins out in the forest to die because they are seen as evil. Another might be their relative acceptance of some domestic abuse, we see that Okonkwo is known for having a bad temper and sometimes hitting his wives, but though it is frowned upon, it is accepted.