This is a very non-supportive argument, but it's still something that could show my perspective. I have the perspective that there is no "good God".
People who are typically happier have a brighter and more faithful perspective of their beliefs whether or not they believe in God, Allah, ect. Gods are usually seen as the epitome of a righteousness ; when you're more happy you can see that righteous God as somebody you need to follow and fully believe in.
Many people grow up in poverty, a broken or abusive family, and in many other bad situations. It would make sense that they don't believe in a "good God" because they've had all of these bad things happening to them. They can look at the world and see all of these school shootings, attacks, and brutal murders; they can see that nobody is really helping control the world. They may grow up in a very Christian society saying that God is looking at us from above and is helping the world that he created, but they can tell he is not doing that. These people realize that God is not good in a way because of the fact that he supposedly created the world like this. These people can believe that the world is just a living hell in itself and this fantastic all-knowing God created that hell.
This world is full of death, violence, and lies. These people are honestly really lucky to realize that. It may have taken a lot to have realized it, but they get to see the truth about the world. They get to see that God is not technically "good".
The happy people are lucky to have what they do as well. They're blinded by the horrible things within the world sometimes and they had a happy nice lifestyle. The only downside to what they have is the fact that they're sometimes too blinded. They're too blinded by their happiness and greed to keep that happiness.
The people who struggle, may not realize this but their sins are covered with sins are the people that reach up to god, are the one's that live in his joyous kingdom. But the people who hate his perfect world and tell him, are the one's that are not as happy, but god forgives the sinners.
Often those who suffer the most have the strongest faith. The people who have gone through comparatively little deny God.
I give you the examples of Bonheoffer, Corrie Ten Boom, Elisabeth Elliot, and millions of others who were tortured and killed for their faith.
Perhaps Atheists are bitter at God for the death of a family member, but the harshest aspects of life do not ruin a faith, but strengthen it.